The do statement, the simplest form of do group processing, designates a group of statements to be executed as a unit, usually as a part of ifthenelse statements. How can a beginning sas programmer write less sas code for this type of data preparation that is also more efficient. For most interactive procedures, you execute statements by submitting a run statement. The sas statements are repeatedly executed until the while condition becomes false. Do until loops continue executing until the condition you have specified becomes true. Fehd, centers for disease control, and prevention, atlanta, ga, usa. The do until statement executes statements in a do loop repetitively until a condition is true, checking the condition after each iteration of the do loop. Included are examples of do and array statement shortcuts. These are basically two loops which are do while and do until. Writing cleaner and more powerful sas code using macros myweb.
List processing with proc sql is also simple, yet powerful. Do while loops continue executing while the condition you have specified remains true. Learn how to use doloop, dowhile and dountil in sas. How to use character values on a macro %do loop sas. Sas do loop sgplot posted 01262018 1024 views in reply to anlyng if you change your sgplot procedure to use a by statement you can use the newfile option on the ods pdf statement to generate a new file for each by group. This paper presents a simple dynamic programming technique, the %do loop. Resolving macro variables in quotes within proc sql passthroughs.
Sas do loops in proc ds2 proc ds2 is a new sas proprietary programming language with full release in version 9. Fehd, centers for disease control, and prevention, atlanta, ga, usa abstract the sasr macro language is simple, yet powerful. Unlike most other sas procedures, proc report has the ability to modify values within a column, to insert lines of text into the report, to create columns. But you can use the % do loop in a macro like the following to accomplish this. I have a list of variables i want to do a proc summary on. Question 2 open a new programming window to create mac01. Loops in sas different loops in sas with their examples educba. It discusses statistical and computational algorithms, statistical.
It is hidden in the do l statement, line 21, and happens between lines 22. We use a do loop to perform the data manipulations on the arrays. The do until statement executes statements in a do loop repetitively until a condition is true. This paper demonstrates how to use macro nested macro call, %do %until loops and ods output delivery system to create an automated backward model selection process for proc genmod which does not come with model selection. Although most sas data step programmers have made use of do loops and arrays, few. Posted 04082010 1624 views in reply to qli sort your input data, then in a data step, assign a new sas variable with an incrementing value to represent each unique grouprange, and each time the current observation has exceeded your previous grouprange, increment the new variable. Select variables to transpose with the var statement. The iterative do statement executes a group of statements repetitively based on the value of an index variable. The data step retrieves and helps in the manipulation of the data.
Using do loops there are four forms of the do statement. The set of variables is then referenced in the data step by the array name. Arrays and do loops are efficient and powerful data manipulation tools that you should have in your programmers tool box. Do loop proc freq posted 091720 2687 views in reply to hsharma i would look at the table in sashelp. As these proc summaries are performed individually per variable, it would be faster for me if i can find some way to loop through a numbered list of variables, then create an output to excel or simply a combined table of results that clearly indicates what results belong to what variable. It discusses statistical and computational algorithms, statistical graphics, simulation, efficiency, and data analysis. A beginners guide to arrays and do loops sas institute. The other type of do loops that you can run in a sas data step are conditional do loops. All price values for all price1through price17 will be increased by 10%.
Data statement sas statements do statement iterated sas statements end statement sas statements run statement do loop processing you can use do loops to perform repetitive calculations. Sas performing loops in a proc step stack overflow. Dec 12, 2011 proc iml is also an interactive procedure. Within a data step, a do loop is used to specify a set of sas statements or operations that are to be performed as a unit during an iteration of the loop. Sas do loops so we have now defined our array, but now we have to use it to manipulate the data. Do loop, do until, dow loop, array statement, dim function, set statement options introduction although most sas data step programmers have made use of do loops and arrays, few take full advantage of the power and flexibility of these tools. The difference between the loops is based on the fact that the do while loops continue executing until the condition for the loop is true, whereas the do until loop will execute till the specified. It is understandable that some programmers look at the simulation algorithm and want to write a macro loop for the repeat many times portion of the algorithm. In previous examples, the %do loop is used to generate single sas statements. Im new to sas, and im having trouble with do loops.
A quick intro to sas arrays and do loops gopinath narasimhan saskatchewan cancer agency march 12, 2014. For example, in scl programs, you can use do loops, ifthenelse statements, comparison operators such as eq and lt, and sas macros. In the example above, sas would automatically calculate the number of variables in array. An alternative method is to utilize the implicit loop in the data step with the execute routine to generate a series of macro calls. Do loops in sas iml software a basic iterative do statement in the sas iml language has exactly the same syntax as in the data step, as shown in the following proc iml statements.
His areas of expertise include computational statistics, simulation, statistical graphics, and modern methods in statistical data analysis. The macro function %str can be used, for example, to pass an entire statement into a macro. There are many variations of the do statement and these can be used in. Do loop processing do loop processing statements within a do loop execute for a specific number of iterations or until a specific condition stops the loop. A neat feature of arrays is that sas can count the number of variables. Arthur li, city of hope national medical center, duarte, ca. Sas do while loop this do while loop uses a while condition.
Loops in sas different loops in sas with their examples. Arrays list the variables that you want to perform the same operation on and can be specified with or without the number of elementsvariables in the array. Sas arrays and macros make processing claims with multiple. For example, price2 in observation 5 will now be 126. To check that the new variables were created, we run a simple proc contents after the data step. How to prepare for the sas certified specialist base programming exam. May 11, 2020 rick wicklin, phd, is a distinguished researcher in computational statistics at sas and is a principal developer of proc iml and sas iml studio. Simplifying your %do loop with call execute sas support.
Since macro do loops cant handle fractions, i used 100 to 200 by 25, rather than 1 to 2 by. Using the count function with a do loop in the data step to create a sas data set consisting of programming language, and the. The technique you want to use is called the uniqueloc technique. The do statement designates a group of statements that are to be executed as a unit, usually as a part of ifthenelse statements. When coupled with a sas array, do group processing simplify the data manipulation process even further. The sas iml language is a matrixvector language, so statements that operate on a few long vectors run much faster than equivalent statements that involve many scalar quantities. Do loop do loops are executed usually repeatedly according to directions that are specified in the do. The do statement, the simplest form of dogroup processing, designates a group of statements to be executed as a unit, usually as a part of ifthenelse statements. Sas will count the number of variables and then define the array with that number. Department of commerce abstract boilerplate sas programs are real time savers, but frequently input datasets have different variables and values not accounted for in the code. Use do loops to eliminate redundant code and to perform repetitive calculations. I have some advice on using do loops in sas iml language. Do loops begin with a do statement and end with an end statement.
Lets look at a couple examples where a basic iterative do loop can be used. Also, since sas dataset names can only contain alpha, numeric and underscore characters, rather than try to create an illegal name that contained a. Conditional loops in sas are the other do loops that are executed over in data steps. Do you often need to transpose your data sets from long multiple rows per subject to wide multiple columns per subject. You can also iterate backwards by using a negative value for the by option. Carpenter california occidental consultants abstract one of the unique features of the report procedure is the compute block. Given below is the general form of a do loop statements in sas.
If you have experience writing data or proc steps in the base sas language, the basic elements of scl are familiar to you. The until test is evaluated at the bottom of the loop. The % do loop is replaced with a sequence of text that follows the create table command. Sep 07, 2011 avoid unnecessary loops in the sas iml language. Sep 07, 2011 avoid unnecessary loops in the sas iml language i have some advice on using do loops in sas iml language. Examples of do loops in sas with proc ds2 quanticate. But when you want the same set of statements to be executed again and again, we need the help of loops. Sas programmers often need to create labels for a numbered series of variables with a common prefix. Jul 18, 2012 you can program this simulation in two ways.
I was given the additional statement, the %do loop isnt within a create table command. Proc iml is unusual in that you do not need a run statement in order to execute sas iml statements. The %do loop is replaced with a sequence of text that follows the create table command. Array and do loops can not be used here since the label statement is a declarative statement. Jun 05, 2019 rick wicklin, phd, is a distinguished researcher in computational statistics at sas and is a principal developer of proc iml and sas iml studio.
There are two forms of conditional do loops, do until loops and do while loops. Interactive procedures remain running until you submit a quit statement, or until you submit a new proc or data step. The sasiml language is a matrixvector language, so statements that operate on a few long vectors run much faster than equivalent statements that involve many scalar quantities. Where the x1 variable contains the x1 value, x2 contains the x2 value, etc. Do group a do group is a sequence of statements that starts with a simple do statement and that ends with a corresponding end statement. Proc iml is unusual in that you do not need a run statement in order to execute sasiml statements. K3 do iterate compare the iteration with the do until and do while examples above. I have some advice on using do loops in sasiml language. It enables you to loop over unique values of a categorical variable in this case, unique cities and do something for each value in this case, copy the distance into another array. Arrays and do over loops are a way of programming more. Do loops in proc ds2 fred ross, quanticate international ltd, manchester, united kingdom george allerston, quanticate international ltd, manchester, united kingdom rachel linacre, quanticate international ltd, hitchin, united kingdom abstract proc ds2 is a new sas proprietary programming language with full release in version 9. I moved your ods output and proc append inside your loop, so the ods table will be appended with each loop. Top 50 sas interview questions for 2020 sas training edureka.
To have sas do the counting, put a in the brackets instead of the number of elements. Rick wicklin, phd, is a distinguished researcher in computational statistics at sas and is a principal developer of proc iml and sasiml studio. A typical sas program can be divided into two steps namely the data step and proc step. Do loopsdo loops are used when a statement or set of statements needs to be repeated many times. One often uses an iterative % do loop to execute a section of a macro repetitively.
It can also be used to dynamically build a series of data steps or proc steps. Sas arrays a sas array is a set of variables of the same type that you want to perform the same operation on. You could also do it in graph template language, dynamic variablesconditional templates which for this example might be a bit overkill, but it is well worth learning for more complicated graphs, good help is. The following program uses a do loop to tell sas to determine what four times three 4. I was given the additional statement, the % do loop isnt within a create table command.