Handout 6 working with retain and sum statements in sas. This paper will demonstrate the power of using retain statement in the following daily programming work. This course focuses on both the practical application of sas code as well as exam questions that commonly appear in the exam. The features provided by sas stat software are in addition to the features provided by base sas software. Sum and retain when defining a new variable in a data step, sas sets the value of the new variable to missing when it jumps to the next observation. Effective use of retain statement in sas programming.
Which one of the following is true of the retain statement in a sas data step program. Otherwise, sas automatically sets such values to missing before each iteration of the data step. Please note that the sas student license and media expires annually in june. It is a declarative statement, not an executable statement. Retain statement instructs sas not to reinitialize values to missing for the variables specified in the retain statement. There is an implicit retain statement in this statement. Top 30 sas interview questions and answers software testing.
Sas has a very large number of components customized for specific industries and data analysis tasks. This video shows you how to use first, last, and retain keywords in a sas data step to manipulate data and get the information you need. Retaining, lagging, leading, and interleaving data pharmasug. If you follow the variable name with a number, the value of the retained variable will be initialized to that number. One approach ive had success with as an interviewer, is to provide interviewees with a real sas program related to the job they are applying for. The power of retain statement in clinical trial programming. Likewise, if the observation is the last in a by group, sas sets the value of last. When the processing of the data step reaches the next observation, the held value represents information from the previous observation.
When sas reads the data statement at the beginning of each iteration of the data step, sas places missing values in the program data vector for variables. I just had to delete the visit for the by statement and it worked. The retain statement, if suitably positioned, is a straightforward way to arrange the order of variables in a sas dataset to meet external requirements. An observation is written to the output datasets if no output statements are used in the data step. The retain statement simply copies retaining values by telling the sas not to reset the variables to missing at the beginning of each iteration of the data step. Please explain what youre trying to do in detail and maybe we can offer alternate solutions. Qtrsasdate extracts the quarter from a sas date and returns a number from 1 to 4. A more efficient method compares the revenue from all observations in a single data step. The power and the trap of automatic retain lex jansen. Specifically, it addresses the retain statement and lag function as used to. Dictionary, and the sas procedures guide for documentation of base sas software.
Program 16 shows the corrected version of this program with the retain statement added. As i understand the retain statement is a global statement so it can appear anywhere in the data step. In this paper i will discuss the retain statement in detail but, of course, not exhaustively. Could any one help me out how to retain a variable in proc sql like how we do in base sas. Onestop guide to data manipulation in sas analytics vidhya. Class contains variables name, sex, age, height, and weight in that order. Monthsasdate extracts the month from a sas date and returns a number from 1 to 12. Highresolution plots require proc gplot in sasgraph software. The sas certified specialist exam prep course is the complete prep course that covers the rest of the exam topics for the sas certified specialist exam. Using retain statement in sas solutions experts exchange. All sas functionscan,find,cat,input,put,tranward,substr,trim,strip,char. The retain statement is used to keep a specified value assigned by an input or assignment statement from the current iteration of the data step to the next.
The retain statement allows values to be kept across observations enabling complex. Within a sas program, when it is required to move from the current iteration to the next of the data step, at that time retain statement tells sas to retain the values rather than set them to missing. The calculation in the compute total block for the total computed variable shows the weight variable without the statistic of. It is also commonly used to determine column variable position in a sas data set, and to assign initial values to variables. Audience this tutorial is designed for all those readers who want to read and transform raw data to produce insights for business using sas. Without a retain statement, sas automatically sets variables that are assigned values by an input or assignment statement to missing before each iteration of the data step. Introduction to sas programming university libraries.
Sas software is used for both a graphical interface and the sas programming language. Lisa fine, united biosource corporation, ann arbor, mi. This article will demonstrate how the retain statement works and provide a series of. Variables not listed in these statements retain their original position. Using a value in a later observation sas institute. The variable is automatically declared the first time you specify it in an assignment statement. Jan 20, 2020 this video shows you how to use first, last, and retain keywords in a sas data step to manipulate data and get the information you need. Take values of previous observation to next observation so that we can do comparison to previous values.
For all other observations in the by group, the value of last. Apr 16, 2020 within a sas program, when it is required to move from the current iteration to the next of the data step, at that time retain statement tells sas to retain the values rather than set them to missing. You cant use retain or anything similar in proc sql afaik. The features provided by sasstat software are in addition to the features provided by base sas software. Use a retain statement to specify initial values for individual variables, a.
The retain statement is one method that sas programmers commonly use for making comparisons across observations. Sas software than comparisons within an observation. Sas retain statement not working as i hoped stack overflow. The retain statement allows for comparisons between observations in a sas data step. Learn and practice sas without going back and forth between the training and the coding interface. Sas statistical analysis system is one of the most popular software for data analysis. So once output the variable base has been created which contains the retained value. In sas, you do not have to declare a variable before assigning a value to it. Base sas software is an easytolearn fourthgeneration programming language for data access, transformation and reporting. Create a new variable using an assignment statement. The retain statement causes a variable that is created in the data step to retain its value from the current observation into the next observation. Explorer is for displaying data sets and results is for displaying result titles. The retain statement causes a variable that is created in the data step to retain its value from the current observation into the next observation rather than being set to missing at the beginning of each iteration of the data step.
Use a retain statement to specify initial values for individual variables, a list of variables, or members of an array. How to prepare for the sas certified specialist base programming exam. Only the variables whose positions are relevant need to be listed. Apr 27, 2019 likewise, if the observation is the last in a by group, sas sets the value of last. Sas base programming certification science flashcards quizlet. The retain statement has no effect on retaining values of existing variables being read from the data set. Program 11 demonstrates a sas data step where a retain statement is not used. The retain statement does not, will not, and unless the underlying sasbase code is rewritten can. An observation is written to the output datasets if no output statements are used in. You must first run the logistic procedure to fit the desired model. You will need to use a sorted input file and use a by statement with the key variables, and retain the important variables using the if first. The retain statement is often a mystery to beginning sas programmers.
Create sample data the following program creates a sample data for. However, those initiated will quickly tell you that the retain statement does not retain. It is widely used for various purposes such as data management, data mining, report writing, statistical analysis, business modeling, applications development and data warehousing. Nov 04, 2019 only the variables whose positions are relevant need to be listed. In summary, the retain statement can be used in novel ways to circumvent problems that commonly arise in the process of programming. Using retain statement in proc sql sas support communities. In sas, its a very easy and useful way to retain values with retain statement. Feb 20, 2018 normally at the end of the data step several things happen automatically, among those are. Suppose you have a data set mydata with variables in the order of e c a b d. That is, it will continue to be the initialized value until it is replaced by another value. For more information, see attrib statement in sas data step statements. Aug 02, 2017 if the scree plot contains an elbow a sharp change in the slopes of adjacent line segments, that location might indicate a good number of principal components pcs to retain.
Libname libref engine sasdatalibrary libref is 1 to 8 characters long beginning with a letter or underscore and containing only letters, numbers, or underscores engine is the name of the library engine used in the os sasdatalibraryis the name of the library where files are stored. Many data management and reporting capabilities you will need are part of base sas software. The next statement tells sas the grouping variable. The retain statement does not, will not, and unless the underlying base sas code is rewritten can never retain anything. If the scree plot contains an elbow a sharp change in the slopes of adjacent line segments, that location might indicate a good number of principal components pcs to retain. Retain statement is a commonly used statement in clinical trial programming. The length statement is specified before the set statement.
Base sas software to generate lowresolution plots via proc plot. Year sasdate extracts the year from a sas date and returns a fourdigit value for year qtr sasdate extracts the quarter from a sas date and returns a number from 14 month sasdate extracts the month from a sas date and returns a number from 1 to 12 weekday sasdate extracts the day of the week and. In summary, the by statement in the data step automatically creates two indicator variables. It is just easier if you set the value into a variable first and then conditionally use the variable. Understanding the retain and count functions in sas lex jansen. Sas tutorial for beginners to advanced practical guide. Training course for beginners and learn how to code your first sas program. This is why sas does not reset the value of count to missing before processing the next observation in the data set. Via apis, you can load data into memory and apply cas actions to transform, summarize, model and score data. The retain statement keeps the value once assigned.
You are still no better off trying to demonstrate your sas knowledge. When you have existing data in sas and want to change the order of the variables, use the retain statement. Other than the retain statement that is used to instruct the sas system not to assign. Exploring the secrets behind one of the most popular procedures in base sas software, continued 3 in the preceding code, the define statement for the weight variable lists mean as the statistic.
Base sas is used to manage and manipulate the existing data for further analysis. If you had taken the time to read the documentation, you would not have posted this question. Weekdaysasdate extracts the day of the week from a sas date and returns a number from 1 to 7, where 1 represents sunday, and so on. It provides a webbased interface, programs for data manipulation, information storage and retrieval, descriptive statistics and reporting, a centralized metadata repository, and a macro facility. To understand how the retain statement works, you must first understand the basic operation of the sas data. Year sasdate extracts the year from a sas date and returns a fourdigit value for year qtr sasdate extracts the quarter from a sas date and returns a number from 14 month sasdate extracts the month from a sas date and returns a number from 1. By default, sas initializes variable values to missing after each iteration of a data step until a value is assigned through an. The retain statement is most often used to reorder variables simply because no other variable attribute specifications are required.
It includes many basic concepts of sas basic concepts of the sas to program efficiently. So now you understand the retain statement, but in the next interview they ask you about the lag function that youve never used. One source of misunderstanding around the retain statement centers around how long a value is retained and the ability or. Normally at the end of the data step several things happen automatically, among those are. When reading raw data, sas sets the values of all variables equal to missing at the start of each iteration of the data step. If you would not use retain statement then sas would return missing at the beginning of each iteration. You can use the variables to determine the first and last record in each by group.
Sas certified specialist base programming prep course. Sep 15, 2019 the retain statement causes a variable that is created in the data step to retain its value from the current observation into the next observation. Two data step statements can prevent sas from setting the new variable to missing, and instead, let it carry its current value on to the next observation. It tells sas to not to read a new record when an input statement is encountered. Let us print a program that will display the output value of z starting from 1 by using the retain statement. Assigning initial values use a retain statement to specify initial values for individual variables, a list of variables, or members of an array. By default, sas initializes variable values to missing after each iteration of a data step until a value is assigned through an input statement or other assignment statement. How can i create an enumeration variable by groups. In the most general terms, the retain statement is used to keep retain values from one observation to the next during iterations of the sas data step.
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