# How To Fill Missing Values In Dataset

Data is missing completely at random (MCAR) if the event that leads to a missing data is independent of observable variables and of unobservable parameters. It is recommended to preserve the original raster datasets wherever possible, so the Mosaic tool and the Mosaic To New Raster tool with an empty raster dataset as the target dataset are the best choices to merge raster datasets. If your data contains gaps – data points without values – you can easily make the chart display a gap as well. Best, John. Create a new Console Application in Visual C#. Sometimes you would like to carry the last value forward, you can then use tidyr::fill. TestTable where wlr. I need to find the median of each column whilst somehow not selecting the title of the column. Now, head over to the next step. Downloads. It can be more sensitive to extreme data values than the median. my code attached here in this code foreach (DataRow dr in table. Missing Value treatment becomes important since the data insights or the performance of your predictive model could be impacted if the. The MySQL manual explains how this works, so I don’t want to go into it; I just want to point out that you should expect odd values. Essentially, what we are looking to do is to filter our data based on a letter grade value in the range of data in column B. fillna( 'NA' ) This way, the vectorizer will create additional column =NA for each feature with NAs. In the attached Excel workbook, "NULL and Missing Examples. It is a fixed collection of same data type that are stored contiguously and that are accessible by an index We specify their length and we can initialize arrays with data. Thank you for taking the time to write it. I am using the following classifiers: J48, SMO, IBk, RandomForest,. If some data are missing, it is not possible to assess the correlation in the usual way. In this example, you see missing data represented as np. Then, the report should work as desired. replace: If data is a data frame, a named list giving the value to replace NA with for each column. Dealing with Missing Values. Python - NetCDF reading and writing example with plotting by Chris Slocum is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3. Data Analysis Code Book. How to Extract the Missing Values through VBA In this article, we are going to create user defined function to find out the missing number in a range through VBA in Microsoft Excel. You have to pass it the DataSet to export and path to where file should be generated. All series operations automatically propagate or handle missing data. , you have no missing values or outliers), or you are performing some of the more straightforward statistical tests, you may only need to know the basics of data setup (see Data Setup and Entry). I’ve been writing quite a few dashboards these days with the flexdashboard package, and in that environment plotly interactive charts are more informative than static ones. Then once I have the median of that row I need to replace all potential 'NA's with the median of the corresponding column! Link to image of dataset. If Fill finds that a primary key exists for a table, it will overwrite data in the DataSet with data from the data source for rows where the primary key column values match those of the row returned from the data source. Sometimes you want to replace these values with some other quantity. I want to fill the missing value of SEX COUNTRY and PERIOD with the previous value, until it changes. stat_Start BETWEEN DATE_SUB(NOW(), INTERVAL 1 HOUR) AND NOW() GROUP BY LEFT(s. "; there are 26 additional missing-value codes denoted by. DataFrame into an xarray. - Replacing the NULL values with average values of the responses from the other records of the same field to fill in the missing value. Here, we either delete a particular row if it has a null value for a particular feature and a particular column if it has more than 70-75% of missing values. Remove Missing Data. n/a for categorical or 0 for numerical values; Substitute the missing numerical values with mean figures; For categorical values, you can also use the most frequent items to fill in. My practical experience suggests that most of the usual solutions (remove rows, impute, pick an algorithm that just miraculously deals with it) are not good. Missing values cannot be compared to any value as NAs are not assigned a value--it simply is or it isn't. SAS Macro to fill missing values in a dataset with specified values for numeric and character values. When a survey has missing values it is often practical to fill the gaps with an estimate of what the values could be. The results: each sample in the data set contained 16 frames in total, 14 of which. Optionally, users may directly upload a distance matrix on which to match. To enter a missing value in a numeric column, do one of the following: Delete the existing value from the cell. Next, select only the empty cells. Define your missing value. This How-To will walk you through writing a simple Python script to see if your data set has null or empty values, and if so, it will propose two options for how to modify your data. Once again, you come to my rescue! I was doing exactly as you describe in the first paragraph – falls data – and needed to pad zeros. In R, missing values are often represented by NA or some other value that represents missing values (i. It's an array and the NaN values are missing. This is OK if this only causes the loss of a relatively small number of cases. The fillna function can "fill in" NA values with non-null data in a couple of ways, which we have illustrated in the following sections. Create a DataFrame from the customer data using the previous recipe, and then try each of the following methods. IS MISSING Operator : Selecting Missing Values Task 4 : Suppose you want to select only those observations in which students did not fill their section information. If you do not need this data then do nothing. There are several ways you can use for handling missing values in your dataset. Then once I have the median of that row I need to replace all potential 'NA's with the median of the corresponding column! Link to image of dataset. Usually it comes from some web reports or accounting programs output, where applied report criteria or other important data forms a header rows of report. How to fill in missing data with a simple formula In this video, I'll show you a way to quickly add missing data to a worksheet. Check that after you substitute these values into the slope formula that the slope equation reads 1 = (0 - Y1)/(0 - 1). Question: (1) Fill In The Missing Data By Referring To The Above Data. That is to say, when one or more values are missing for a case, most statistical packages default to discarding any case that has a missing value, which may introduce bias or affect the representativeness of the results. We can add 'Group By' step to group the data by Product values (A or B) before running 'fill' command operation. Eliminating simply we remove the corresponding features (columns) or samples (rows) from the dataset entirely that have a certain number of. The results: each sample in the data set contained 16 frames in total, 14 of which. You will find a summary of the most popular approaches in the following. For example, when you merge documents that include information from various companies, you can include an image of each company’s logo as part of the merge. Missing Value treatment becomes important since the data insights or the performance of your predictive model could be impacted if the. Missing data management. If the analyst must discard an entire record because the value for one variable is missing, valuable information is lost. Using a function will be quicker than. RapidMiner Studio has many different operators to help you increase your data quality but for this post, we'll focus on replacing missing values and replacing values. We can see that the mean value for air_temp 9am matches the mean value computed in the summary statistics of the data frame where the missing values were removed. Raster dataset attribute tables Raster datasets that contain attribute tables typically have cell values that represent or define a class, group, category, or membership. Determine how many values are missing. This is then passed to complete() function. There are cartodb and mapbox which are great for creating server-“baked” tilesets, leaflet and d3. In this way, nonmissing values are copied in a cascade down the current sort order. Notice that if a previous value is not available during a forward fill, the NA value remains. Note that the test happens after white space is stripped from the input, so na. cases() returns a logical vector indicating TRUE if all cases are complete and FALSE otherwise. Using Forward fill and Backward fill Backward fill or ‘bfill’ will fill the NaN values with the previous non-null value. So, we have handled the missing data. There are three types of missing values (Allison, 2001): data missing completely at random (MCAR), data missing at random (MAR) and data not missing at random (NMAR). User Defined Function : Microsoft Excel allows you to create your own function as per the requirement, we call it User Defined Function. For spatiotemporal data, you can also use neighbors in time to fill in the missing values. You can set constraint information for a DataTable by using the PrimaryKey and Unique properties. I thought it would hang up since there is a parameter in the dataset but it doesn’t, it selects everything in the list. To explore this, let’s go back to our original dataset we talked about in the first post of this data prep series. Using the concepts of filling discussed in the ReIndexing Chapter we will fill the missing values. First I'll use a formula, then Excel's Find and Replace function, and finally the often-overlooked Go To Special. Show Zero Values In A Pivot Table November 15, 2011 by Barbara Recently a colleague was having an issue with their Pivot Table, they claimed some if their data was ‘missing’, a subscriber to my newsletter also had this issue so I thought I would cover it in today’s post. You can try this on the built-in dataset airquality, a data frame with a fair amount of missing data:. This is an algorithm that does not work when there are missing values in the dataset. For example, I have data from the World Bank on government deficits. Simply replacing the missing value of a predictor with the average value of that predictor is. Hence missing values have to be filled. Practical Strategies to Handle Missing. 8 thoughts on “ Padding and Working with Null or Missing Values ” stacey February 7, 2014 at 11:56 am. The objective of this presentation is not to. You can use Excel to project values that are based on existing data or to automatically generate values based on linear or growth trend calculations. Once the formats have been created, you can continue to use them throughout your SAS session, making the format a very efficient and powerful tool. cases() returns a logical vector indicating TRUE if all cases are complete and FALSE otherwise. data API enables you to build complex input pipelines from simple, reusable pieces. I tried using a calculated field with some LOD, but once the data is null, the calculated field automatically get's a null ( or 0 after using ZN() ), I think the only thing that will solve my issue is to be able to manually fill those missing dates in the table, but Tableau doesn't allow it and the data itself is too big, so modifying it will take eternity. To replace all occurrences of a specified value, use the global (g A2A. There are a number of different ways to impute data when you have missing values. There are applications where a scaffold data set may still require blending, for example; when trying to represent values from multiple data sources a scaffold can be useful to fill in gaps in both data sources. dropna Fill in missing in preTestScore with the mean value of. About a year ago my answer. o The non-missing coordinates of each polyline must be ordered so as to correspond to consecutive nodes. The CheckBoxList control is used to create a multi-selection check box group. Missing data (or missing values) is defined as the data value that is not stored for a variable in the observation of interest. To find out what values in one list are missing from another list, you can use a simple formula based on the COUNTIF function. You'll find bellow a short summary of all the embeded function and their related parameters. com I was looking for a way to display the value of a parameter inside a Power BI report. A local dentist asks her patients to fill out a questionnaire and mail it back to determine the quality of the care received during an office visit. In this example, the old value of MATH corresponds to the new value of 1: Click on the Add button next to the Old -> New text box: Repeat the process for the remaining old and new values. The presence of Missing Values in a data set can affect the performance of a classifier constructed using that data set as a training sample. I'm interested in "balance" this panel, keeping. Changing the representation of a dataset brings up an important subtlety of missing values. • Does not produce imputed datasets. rm=TRUE to each of the functions. Show Zero Values In A Pivot Table November 15, 2011 by Barbara Recently a colleague was having an issue with their Pivot Table, they claimed some if their data was ‘missing’, a subscriber to my newsletter also had this issue so I thought I would cover it in today’s post. Next, let's look at how we can remove instances with missing values from our dataset. An alternate way of entering these data is given at the end of this chapter. Visualising missing data is important when analysing a dataset. There are over 50 variables which takes too much work to do it manually. It will return NumPy array with unique items and the frequency of it. And when it comes to data, there are tons of things that can go wrong – be it the structure, placement, formatting, extra spaces, and so on. dta" to open the dataset P14. , you have no missing values or outliers), or you are performing some of the more straightforward statistical tests, you may only need to know the basics of data setup (see Data Setup and Entry). 1 Investigating quantity and patterns of missingness We begin by investigating how many missing values there are in the variables included in the dataset, using Stata’s misstable summarize command:. " when importing data in R. Drop column if they only contain missing values. This How-To will walk you through writing a simple Python script to see if your data set has null or empty values, and if so, it will propose two options for how to modify your data. Dataset Parameters are a way to bring some sort of dynamic into your Power Query datamodelling in Power BI. If your Fill Method is Temporal Trend, this number is the number of values that exist in your time series for that Location ID (for instance, if you were only missing one value in your time series, it would report the number of time steps in your dataset minus 1). From more detailed analysis of the data, you may have also realized there is one more column that has missing values - the first_affiliate_tracked column. It is recommended to preserve the original raster datasets wherever possible, so the Mosaic tool and the Mosaic To New Raster tool with an empty raster dataset as the target dataset are the best choices to merge raster datasets. filter_by_attrs (self, \*\*kwargs) Returns a Dataset with variables that match specific conditions. However, the code is a complicated macro that is difficult for a beginning SAS programmer to understand. In a blank cell, enter the formula of =IF(A3-A2=1,"","Missing"), and press the Enter key. Once the data has been imputed the analysts can just use it as though there was nothing missing. User Defined Function : Microsoft Excel allows you to create your own function as per the requirement, we call it User Defined Function. How to fill in missing data without the need of a Scaffold data set - Alteryx by Juliana Camparotti | Oct 29, 2019 Last week at the Data School, we learned how to do Data Scaffolding using Tableau Prep Builder and Alteryx. In this case, we divide our data set into two sets: One set with no missing values for the variable (training) and another one with missing values (test). I want to fill a column with the most up to date values for each student. The following program shows how you can replace "NaN" with "0". I was trying to use a multi-row function, but can't really figure out how to since the row of the data that needs to be copied varies. In C# without using Excel Object we can insert , edit , delete , select etc. Practical Strategies to Handle Missing. I followed your guides to fill the missing values of the sparse depth maps of kitti dataset (I gonna use it as my ground truth in training). Length, 8% missing values in Petal. Remove Missing Data. The first task is to identify missing data and recode it. A point dataset is required to have the following structure:. # ' An R function for filling in missing values of a variable from one data frame with the values from another variable. We can easily work with missing values and in this section you will learn how to: Test for missing values; Recode missing values; Exclude. From more detailed analysis of the data, you may have also realized there is one more column that has missing values - the first_affiliate_tracked column. " Fill in missing values, smooth noisy data, identify or remove outliers and noisy data, and resolve inconsistencies ! Data integration " Integration of multiple databases, or files ! Data transformation " Normalization and aggregation ! Data reduction " Obtains reduced representation in volume but produces the. Once SAS processes all observations in a data set, all subsequent observations in the new data set have missing values for the variables that are unique to that data set. The dataset is modified to include missing values in SECTION variable. Since each sample is measured three times by each operator, the results for each sample use three rows of the dataset. 0 Object Library for read or write to and Excel file. Sometimes you would like to carry the last value forward, you can then use tidyr::fill. 6) Click Next. random (MAR) if the probability of missing data on Y is unrelated to the value of Y, after controlling for other variables in the analysis…For example, the MAR assumption would be satisfied if the probability of missing data on income depended on a person’s marital status,. Thus rates[_n-1] is missing for the first year of each id rather than reaching back to the last year of the previous id. To enter a missing value in a numeric column, do one of the following: Delete the existing value from the cell. Fill-in or impute the missing values. According to get-help new-object "By default, you type the fully qualified name of a. You will find a summary of the most popular approaches in the following. A discussion of cleaning large data sets, focusing on how to fill in missing values in our data sets using predictive analytics and statistical methods. Step 3) Replace the NA Values. Summary Here we have seen how Pandas handles null/NA values, and seen a few DataFrame and Series methods specifically designed to handle these missing values in a uniform way. Further, some people advocate for simple methods like using the mean of the feature when it is missing. Then, the report should work as desired. sales_data. If we use the zero imputation technique the data is what you'd expect: For something more interesting, we can look at splines:. I need to find the median of each column whilst somehow not selecting the title of the column. The COUNTIF function counts cells that meet supplied criteria, returning the number of occurrences found. It also means that the complete measure will be omitted in the case that there are no values for it in any of the rows, which is the reason for our problem. And there you have it; a simple approach to filling in missing data that will perform well, without the need for blending. If any of the cells being averaged contain an error, however, it will cause the entire formula to fail. These plausible values are drawn from a distribution specifically designed for each missing datapoint. Click Next. So I made a ggplot version of what it did. A common feature in fill-in forms is the automation of field entries based on a list item selection. The objective of this presentation is not to. Using SPSS to Handle Missing Data. This is followed by an- other temporal 1 -day interpolation. In our missing data, we have to decide which dataset to use to fill missing values. In numeric columns, missing values are denoted by an asterisk (*). sales_data. If the process generating the data is known to follow a simple curve, and you are confident of the fit, you can project values outside the data range, and even get a meaningful confidence interval for the range that the values could actually be (based on how much variation there is between the data and the curve inside the data's range). Far to many people just delete those records, which often contain useful training data. Missing values - series is desinged to automatically support and handle missing data. two) and then self join that table enough times to reach the desired range length (e. OUT=SAS-data-set creates an output SAS data set in which to put the imputation results. Raster dataset attribute tables Raster datasets that contain attribute tables typically have cell values that represent or define a class, group, category, or membership. The COUNTIF function counts cells that meet supplied criteria, returning the number of occurrences found. - [Instructor] Once you've identified missing data, it's really important to either remove that data or fill in the missing data with a reasonable value. na()) to count how many non-NA’s there are. Its purpose is to add observations to the dataset if there are gaps, but the only non-missing values ever created are in identifier and time variables. We have gone through a number of ways in which nulls can be replaced. Missing values cannot be compared to any value as NAs are not assigned a value--it simply is or it isn't. A Study on Handling Missing Values and Noisy Data using WEKA Tool (IJSRD/Vol. , variances, covariances, and means) are estimated, perhaps using the listwise deletion. Greatly appreciate if you could guide me. mean/median is fine on a small data set but on large data sets with many outliers and missing values, I think it's not a good approach to fill 40-50% values in a column with median/mean. Whether you are using Excel or a Google Spreadsheet, pivot tables are a great tool for summarizing and analyzing large amounts of data. The value must be of the following type: Integer, Long, Float, Double, String, Boolean. That way you can visualize the data set at each step by clicking on the output dot of each module and selecting "Visualize. When analyzing and visualizing a new dataset, you'll often find yourself working with data over time. I searched about imputing the data and i realized that using inference-based. The next step would be to union this joined dataset with the new value with those records that weren't blank in the first place. Explore Popular Topics Like Government, Sports, Medicine, Fintech, Food, More. In this article we discuss how to get a list of column and row names of a DataFrame object in python pandas. Here, we are filling with value zero; instead we can also fill with any other value. For inspecting if any cases have many missing values, we'll create a new variable. R Replace NA with 0 (10 Examples for Data Frame, Vector & Column) A common way to treat missing values in R is to replace NA with 0. There are over 50 variables which takes too much work to do it manually. Why Dataset bound Datagridview not showing latest data from Database. Use a global constant to fill the missing values 4. broadcast_like (self, other, …) Broadcast this DataArray against another Dataset or DataArray. If this assumption holds, resulting estimates (i. This page shows a few methods of looking at missing values in a dataset, this information can be used to make better informed decisions about how to handle the missing values. xlsx", the project "Brosnya" is NULL for "In-Progress" and "Completed". Excel can manage missing data or bank cells when creating scatter or line charts in three different ways: The blank cell is given a value of zero. , regression coefficients and standard errors) will be unbiased with no loss of power. We have 10 missing values in row numbers indicated by the first column. General characteristics of raster data. Create a DataFrame from the customer data using the previous recipe, and then try each of the following methods. In python, if you double click and visualize your data, then you will see the blank data = ‘NaN. Whatever the value of StudentIBFlag is in the most current YearSem, I want that to populate all rows for. Use attribute mean for all samples belonging to the same class as the given tuple. resolve = 'error' , so if you're certain there's no issue, you can speed up execution by setting, say,. Once the data has been imputed the analysts can just use it as though there was nothing missing. The queue stores the new (missing. One of the common tasks of dealing with missing data is to filter out the part with missing values in a few ways. Downloads. Note how the last entry in column 'a' is interpolated differently, because there is no entry after it to use for interpolation. Pandas : Drop rows from a dataframe with missing values or NaN in columns 2 Comments Already Raghu - December 18th, 2018 at 9:33 pm none Comment author #25254 on Python Pandas : How to add rows in a DataFrame using dataframe. The mice package in R, helps you imputing missing values with plausible data values. If you have a simple data set (e. TRUNCOVER does not read a new data line when INPUT does not find values in the current data lines for all variables specified. An educated guess could be that you are charting them and want the missing dates be represented as 0. You learn something new every day. Options are: none - (default) skip rows where a point is missing, inner join. Generating Zeroes in PROC TRANSPOSE Output. 3) Select the Choose an existing dataset in this report or a shared dataset option, and select AnnualGrossProfit. I also used the NYU tool box but the result was too bad (the below picture). I have tried to refer to some examples but still not working my dataset is called mersing which contains 1029 rows and 8 columns. Missing values are part of the game when you are dealing with data in SAS. This command also can be misleading since missing values are essentially taken as Null values and not NA and sum(is. I searched about imputing the data and i realized that using inference-based. 1 Investigating quantity and patterns of missingness We begin by investigating how many missing values there are in the variables included in the dataset, using Stata’s misstable summarize command:. Take a look at the graph. value_counts() Africa 624 Asia 396 Europe 360 Americas 300 Oceania 24 If you just want the unique values from a pandas dataframe column, it is pretty simple. NET though that I had previously running is DataTable serialization I have in use in a few older apps. In my example file I have four variables. Raw: The raw rgb, depth and accelerometer data as provided by the Kinect. various techniques for the estimation of missing values in time series data models. Viewed 2k times 0. SQL JOINs make it easy to find and fix missing data by Jeff Davis in Data Management on April 30, 2002, 12:00 AM PST Many people are confused by various JOIN operations supported by SQL. Generating Zeroes in PROC TRANSPOSE Output. Step 5) A big data set. The answer would depend on the percentage of those missing values in the dataset, the variables affected by missing values, whether those missing values are a part of dependent or the independent variables, etc. To assign serial numbers to observations in a data set in SAS, create a variable using _N_, a system variable, which contains observation numbers from 1 through n. Solve for the missing coordinate by algebraically manipulating the equation such that the missing coordinate variable is on the left side of the equation and actual coordinate value you must solve for is on the right side of the equation. 7) We'll keep the default for Choose Layout page. To get help filling out the four parameters required, go to the INSERT menu and select Function, see Spreadsheet Data 6. This involves two steps. NET using the Excel object You can format your data as a TAB delimited string, use the Excel object to start an instance of Microsoft Excel, select the worksheet and range to populate, and paste in your data. If A is a matrix or multidimensional array, then v can be either a scalar or a vector. All series operations automatically propagate or handle missing data. After learning to read formhub datasets into R, you may want to take a few steps in cleaning your data. 1, use a 4. How to Visualize and Compare Distributions in R By Nathan Yau Single data points from a large dataset can make it more relatable, but those individual numbers don’t mean much without something to compare to. omit(mydata) Advanced Handling of Missing Data. This produces the same result as the first scenario. For example, we'll flag cases that have a missing value on doctor_rating with the syntax below. Remove Missing Data. Missing Data is a very big problem in real life scenario. According to get-help new-object "By default, you type the fully qualified name of a. If I put the cursor into the last column, which contains a full set of values, control A will do the trick. 12 which is the mean of all the values that are available to us. Therefore it’s advisable to fill them in with Pandas first: cat_data = cat_data_with_missing_values. We have 10 missing values in row numbers indicated by the first column. From the main website, we can learn a few things about this publicly available dataset. a) Missing completely at random (MCAR): Suppose variable Y has some missing values. Viewed 2k times 0. Use the attribute mean (or majority nominal value) for all samples belonging to the same class. Periodically, you may have a need to fill in gaps within an Excel spreadsheet. Replace Missing Values with Zero in SAS. Saving Your Data. RapidMiner Studio has many different operators to help you increase your data quality but for this post, we'll focus on replacing missing values and replacing values. At the beginning of the data field name, type an “at” symbol (@) to insert text or paths that refer to image files. Eliminating and Imputing are two different strategies for handling samples or features with missing values. Generally, they revolve around one of two strategies: using a mask that globally indicates missing values, or choosing a sentinel value that indicates a missing entry. Answer: There are codes for refused (7-fill: that is 7, or 77, or 777…, depending on the number of digits required for a particular data value), don't know (9-fill), and missing values (a blank field) which means the person was not asked the question or given the test. This means that you can create a series where values are missing for some keys (e. The process of estimating missing values in time series data for univariate data involves analysis and modelling. In this section, we will try to evaluate a the Linear Discriminant Analysis (LDA) algorithm on the dataset with missing values. Expected Value of an Arbitrary Function. For example if your dataset includes the age of students in a school(but many of those values are missing), an average of values shouldn't create problems for certain analysis. Average is the default value for this property. The y-coordinate values on the line of best fit match the x-values from the data set. Use attribute mean for all samples belonging to the same class as the given tuple. You can fill the values in the three ways. Deleting/Ignoring rows with missing values. Notice that if a previous value is not available during a forward fill, the NA value remains. When analyzing and visualizing a new dataset, you'll often find yourself working with data over time. Dataset Parameters are a way to bring some sort of dynamic into your Power Query datamodelling in Power BI. Hi, I using Weka to classify my data set, which has a lot of missing values, and two classes. Flexible Data Ingestion. In your case, you have an easy task to fill in missing values for a string variable which you know should be constant. This method commonly used to handle the null values. Usually, these tables were sorted manually in Excel, using the Data, Sort command. Fill in Missing Values in an Astronomy Dataset SynthesizeMissingValues allows for missing data to be imputed based on an estimation of the underlying distribution of the dataset. Implicitly, i. Pivot Table Overview. While importing a dataset while making a machine learning model, often we find missing data. The process of estimating missing values in time series data for univariate data involves analysis and modelling. This data has also been preprocessed to fill in missing depth labels. How to pass dataset value into array. Step-by-Step Examples. If the data has missing values, they will become NaNs in the resulting Numpy arrays. Missing values cannot be compared to any value as NAs are not assigned a value--it simply is or it isn't. This selects all cells between those two points. In the above example, missing COL0 and COL2 attributes of TEST_TABLE second row represents null values.