# First and last in sas examples pdf

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- FIRST. and LAST. Variables in SAS – How to Select the Variables
- SAS : First. and Last. Variables
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- FIRST. and LAST. Variables in SAS – How to Select the Variables

Some of the things we can do include:. The following code simply creates a data set in the work library called "j" that is a copy of the data set jjj located in the mat library. The following code concatenates the jjj and mmm data sets as shown. To merge two data sets as shown pictorially we use the following syntax:. Data steps can be used in conjunction with the where statement to select certain variables.

## FIRST. and LAST. Variables in SAS – How to Select the Variables

Our tutorials reference a dataset called "sample" in many examples. If you'd like to download the sample dataset to work through the examples, choose one of the files below:. When preparing data for analysis, you may need to "filter out" cases rows from your dataset, or you may need to divide a dataset into separate pieces.

In this tutorial, we use the following terms to refer to these two tasks:. A subset is selection of cases taken from a dataset that match certain criteria. You can also think of this as "filtering" a dataset so that only some cases are included. When subsetting a dataset, you will only have a single new dataset as a result. A split acts as a partition of a dataset: it separates the cases in a dataset into two or more new datasets.

When splitting a dataset, you will have two or more datasets as a result. Both subsetting and splitting are performed within a data step, and both make use of conditional logic. Both processes create new datasets by pulling information out of an existing dataset based on certain criteria.

The difference between the two processes is in how the cases are selected. Note: A related task is to select a subset of variables columns from a dataset. For instructions on how to drop or keep variables from a dataset, see our Data Step tutorial. Subsets can be created using either inclusion or exclusion criteria.

Inclusion and exclusion criteria are both statements of conditional logic that are based on one or more variables, and one or more values of those variables. The criteria for keeping an observation is called the inclusion criteria.

The "disqualifying" values you specify are called the exclusion criteria. The inclusion or exclusion criteria appear after the IF statement. Let's create a subset of the sample data that doesn't contain any freshmen students. The resulting subset has observations. Can you name what groups of students are included in this subset? Hint: there are four different groups. For example, how would we write the conditional logic for a subset containing only male students, and that live in-state or are at least juniors?

In this case, there are three criteria variables: gender, state residency, and class rank. Every subject included in the subset must be male, and in addition to being male, the subject must either a be an in-state student, or b be "at least a junior" -- i. The code required to make this subset is given below. Notice that you can use multiple sets of parentheses to group conditional statements. The parentheses identify the "order of operations" in terms of how the conditional logic statement is read.

In this case, it's mandatory that everyone in the subset be male; after that, they can either be in-state students or at least juniors. That means that our subset will contain all sophomores, all juniors, all seniors, all students with missing class rank values, and out-of-state freshmen.

Now let's say we want to include only the observations whose Math scores fall between 55 and If you want to make sure that the procedure works, you can compute the mean of the variable from the new dataset and see if the data falls between the specified range. As you can see, the observations for the Math variable are within the 55 to 75 range that we specified. It's also possible to subset your data based on row position. For example, you may want to extract all cases in a dataset beginning at the 5th row, or extract the first 30 cases in a dataset, or extract rows 20 through 30 of a dataset.

For these examples, let's work with the following tiny set of data, so that it's easier to see which rows are extracted in each case:. In this situation, we want to skip over the first rows of the dataset, and keep only the cases from row 6 onward. This situation is the opposite of the previous example: here, we want to keep the first rows of the dataset, up through and including row 6. This implicitly means that we are extracting rows 1 through 6.

In general, if you are able to express the cases you want to extract in terms of one of your variables, it's preferable to use the above IF-THEN approach, rather than telling SAS to extract by rows.

Sometimes you may want to split a dataset into two or more datasets based on the value s of a variable s. In this kind of data step, you create two or more datasets at one time based on one whole dataset. It is an extension of the method described above for subsetting data. The basic code to create two datasets is as follows:. Alternatively, you may wish to partition a dataset by separating all cases with a certain criteria into one dataset, and all cases not meeting that criteria into a second dataset.

This means that the cases in the two datasets will be mutually exclusive and exhaustive. The basic code to partition a dataset in this manner is:. The general code above only shows the case where a dataset is partitioned into two datasets, but it's possible to partition a dataset into as many pieces as you wish. In the DATA statement, list the names for each of the new data sets you want to create, separated by spaces.

Let's illustrate this by splitting the sample dataset into four parts based on class rank, creating one dataset for each class. Note that this block of code does not take into account the cases where variable Rank is missing. That means that the splits in this example were mutually exclusive, but not exhaustive: some of the cases were lost in the split.

Now let's try to partition the dataset so that all freshmen are in one dataset, and all other cases are put in a second dataset.

That means that the second dataset will contain the "not-freshmen"; i. Unlike Example 1, this split will create mutually exclusive and exhaustive datasets; that is, none of the original cases will be lost in the split. Let's compare the first few cases of the new datasets. The new dataset called freshmen should look pretty homogenous with respect to variable Rank :.

Notice that observation 9 student ID 15 has a missing value for Rank. Note that this dataset is identical to the subset that was created in Example 1. Recall that missing values are denoted by a period. Let's try to partition a dataset into missing and non-missing cases with respect to the variable State , which is a character variable.

To indicate a missing character value, we use an empty set of quotation marks "". Recall that quotation marks are used in SAS to indicate strings, so having two quotation marks next to each other indicates a blank string. The first few rows of output should look like this:. You should see that the column containing the cases for State appears completely empty, indicating that all the cases in this dataset have missing observations for State.

Search this Guide Search. Subsetting vs. Splitting When preparing data for analysis, you may need to "filter out" cases rows from your dataset, or you may need to divide a dataset into separate pieces. In this tutorial, we use the following terms to refer to these two tasks: A subset is selection of cases taken from a dataset that match certain criteria. Subsetting Datasets by Conditions Subsets can be created using either inclusion or exclusion criteria.

Example - Delete cases with a specific value Let's create a subset of the sample data that doesn't contain any freshmen students. Subsetting Datasets by Rows It's also possible to subset your data based on row position. Splitting a Dataset Sometimes you may want to split a dataset into two or more datasets based on the value s of a variable s.

Example - Splitting using IF and ELSE statements with logic based on a numeric condition Now let's try to partition the dataset so that all freshmen are in one dataset, and all other cases are put in a second dataset.

The first few rows of output should look like this: You should see that the column containing the cases for State appears completely empty, indicating that all the cases in this dataset have missing observations for State. Report a problem. Subjects: Statistical Software. Tags: statistics , tutorials. University Libraries. Street Address Risman Dr. Contact Us library kent. Facebook Facebook. Twitter Twitter. Flickr Flickr. Instagram Instagram. Youtube Youtube.

## SAS : First. and Last. Variables

Deepanshu founded ListenData with a simple objective - Make analytics easy to understand and follow. He has over 10 years of experience in data science. During his tenure, he has worked with global clients in various domains like Banking, Insurance, Private Equity, Telecom and Human Resource. If you are intersted ,no problem. Data Readin2; set readin; by id; if first. If we have 4 or more than 4 duplicate ids then what would be the logic to find out 2nd observation?

Sex and LAST. The first example shows how to compute counts and cumulative amounts for each BY group. The second example shows how to compute the time between the first and last visit of a patient to a clinic, as well as the change in a measured quantity between the first and last visit. The first example uses data from the Sashelp. Heart data set, which contains data for 5, patients in a medical study of heart disease.

The names of these variables are gmworldwide.orgle and gmworldwide.orgle, where variable is the name of a variable in the BY statement. For example, if.

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You can use this procedure to modify, retrieve and report data in tables and views created on tables. It takes the following general form:. Correspondingly, records are called observations in the previous lessons, but rows in SQL tables; and we call a field of data set as variable, but column in this lesson. The order of these clauses is important. They must appear in the order as shown above.

### FIRST. and LAST. Variables in SAS – How to Select the Variables

For the last observation in a data set, the value of all LAST. Note : It returns first observation among values of a group total 7 observations. Selecting Last Observation within a Group Suppose you are asked to include only last observation from a group. Like the previous example, we can use last. This happens when the value of the variable changes in the next observation. Powerful Analytics. Real Results.

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Understanding how to use the temporary SAS variables,. BY recid gmworldwide.org and gmworldwide.org, is straightforward when there is For example, the analysis may.

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To do this in R, we first order the data and then use the by command. The by command will effectively subset our data based on indicated variables and return an indicated number of observations from the beginning or end "head" or "tail" of that subset. I is data. In This tutorial we will learn about head and tail function in R. IF first.

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