Sas doesnt support that syntax directly, but there is a variant of the do loop in which you can iterate over values in a specified list. An introduction to macro variables and macro programs mike s. The pdf function for the chisquare distribution returns the probability density function of a chisquare distribution, with df degrees of freedom and noncentrality parameter nc. Zdeb, new york state department of health introduction there are a number of sas tools that you may never have to use. Another use of macro functions is when it comes to ignoring certain sas keywords. I have some advice on using do loops in sas iml language.
This paper illustrates how macros were used to scan for the presence of particular words, userids, in output reports to generate a text output file outlining possible problems with hipaa compliance. Unfortunately the fact that the sheets are named with single quotes around them makes referencing a macro variable difficult. This example is roughly 50 times faster than reading in each cell individually in a loop. Simplifying your %do loop with call execute sas support.
However, because the do until expression is evaluated at the bottom of the loop, the statements in the do until loop. Example of %for call with values data source which imports 3 sheets from a. For loops carnegie mellon school of computer science. Importing multiple excel sheets with a macro loop sas. If the expression is false, the statements in a do while loop do not execute. In order to import data from microsoft excel into sas, there are various. The sas ods output statement allows the programmer to save the results from procedure objects to datasets.
So, in each iteration of data, the value of the data step v ariable charvar. If youre getting something else, either the code you posted is different than what youre running, or. K3 do iterate compare the iteration with the do until and do while examples above. Conditional loops in sas are the other do loops that are executed over in data steps. Most people recommend that beginning programmers should avoid learning the macro language, because it is a different language than the data step language. Arrays and do over loops are a way of programming more. Using do loops there are four forms of the do statement. These conditions include a start value for the index variable, a stop value, and an increment value.
Repetitive coding compare the interest for yearly versus quarterly compounding on a. Writing macro do loops with dates from then to when ronald j. Sas has unique features for datadriven programming. Macro functions process macro expressions, called arguments, to produce a new expression. The companion function to the input function is the put function. In the rst example, suppose we are given numerous vectors, say 10, and asked to perform a t test on all possible pairs. For example the variable age is the same as variable age or. Variables will retain their values in the pdv until they are replaced by the new values from the input dataset.
Its value functions as an index that determines the number of times the % do loop iterates. The collection of functions and call routines in this chapter allow you to do extensive manipulation on all sorts of character data. Fehd, stakana analytics, atlanta, ga, usa abstract description. Kahane, westat, rockville, md abstract the sas data step is one of the primary me. Sas programmers often need to create labels for a numbered series of variables with a common prefix. These are basically two loops which are do while and do until. Character functions 3 introduction a major strength of sas is its ability to work with character data. In the code below, proc freq is executed within two nested %do loops inside a macro, and the macro onerec is called to further process the output datasets.
Loops in sas different loops in sas with their examples. Sas do index loop this do index loop uses a index variable for its start and end value. This illustrates each of the steps in the pseudocode looprepeat algorithm shown above. Hence identifying loops in cfg is generally more challenging than detecting cycles. Sas loops you may encounter situations, when a block of code needs to be executed several number of times. A data step do loop populates a sas dataset for each day from that date until today. Examples of such tools are arrays, macros, and quite possibly proc sql. One often uses an iterative % do loop to execute a section of a macro repetitively. The until test is evaluated at the bottom of the loop. In this article, we will discuss differences between iterative do loops and conditional do loops. If you are used to conditionally processing statements in a doloop in sas, there is no real. Ron cody is the author of learning sas by example 4. While data step functions are applied to values on a vector of variables, macro functions are used to create, modify, and work with text strings.
If the macro is writing values into the worksheet, vba will need to wait until the worksheet is. Maplewood new jersey 34509, 3 write sas code that simulates 10,000 numbers from the normal distribution and calculate the mean and. The first time the loop processes, the value of count is 1. It is hidden in the do l statement, line 21, and happens between lines 22. 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. My goal is to demonstrate some useful applications of a number of my favorite functions. Sep 07, 2011 avoid unnecessary loops in the sas iml language i have some advice on using do loops in sas iml language. However, for more complicated tasks, sas has quite a few daterelated functions. Writing macro do loops with dates from then to when. The do statement designates a group of statements that are to be executed as a unit, usually as a part of ifthenelse statements. The variables referenced by the array are called elements. The other type of do loops that you can run in a sas data step are conditional do loops.
In this chapter we will see how to program macros in sas. Since dates are numbers, you can do simple things like subtract two dates to find the number of days between them, without any problem. Array and do loops can not be used here since the label statement is a declarative statement. Do while loops continue executing while the condition you have specified remains true. However, without some proper training it is difficult to implement, or when it is implemented it often results in hard to understand code. Nesting sas macros marsha weston sra international, inc. Syntactically speaking, while sas programming loops or doloops always reside within sas data step, sas macro loops or %doloops are located within sas macros. The sas statements are repeatedly executed until the final value of the index variable is. The iterative do statement executes a group of statements repetitively based on the value of an index variable. Note that do iterative statements also called do loops are often used in conjunction. Jun 11, 2017 java project tutorial make login and register form step by step using netbeans and mysql database duration. Except for t, f, and normalmix, you can minimally identify any distribution by its first four characters.
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. Data step variables into macro variables, and symget does the converse. Syntactically speaking, while sas programming loops or do loops always reside within sas data step, sas macro loops or % do loops are located within sas macros. Sas data integration studio take control with conditional.
Arrays and do loops are efficient and powerful data manipulation tools that you should have in your programmers tool box. 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. When creating a sas dataset based on a sas dataset, sas sets each variable to missing in the pdv. This function accepts noninteger degrees of freedom. An alternative method is to utilize the implicit loop in the data step with the execute routine to generate a series of macro calls. Identifying loops is a wellbuilt problem in controlflow analysis area.
Hey there, so ive been spinning my wheels at this for way too long that i feel like there must be a better way. The %nrstr call prevents macro variable substitution in the do code before the. Tutorial on loops and functions september 28, 2007 this tutorial gives a few examples of typical uses of loops in simple data analysis problems. The main reason is that you can usually reach the same result without them. A beginners guide to arrays and do loops sas institute. Range, cells and application as efficiently as possible outside of loops. Basic array concepts the array statement defines variables to be processed as a group. Apr 30, 2014 sas programming tutorials for beginners by priya sas online training for complete sas programming duration. Loops in cfg have more attributes than simple cycles, such as nesting, multientry and irreducibility. Different languages use different keywords to define the iteration statement.
Print 10 times print the even numbers between 10 and the value of n while and do loops are more natural when we want to keep looping until some outcome indefinite or result controlled loops. Arthur li, city of hope national medical center, duarte, ca. Initially this may seem like a minor difference, but because macro functions deal with text, they can be. At the beginning of the fourth iteration, the value of count is 4, which is found to be greater than the stop value of 3 so the loop stops.
If the macro variable specified as the index does not exist, the macro processor creates it in the local symbol table. The do while statement evaluates the condition at the top of the loop. Effectively utilizing loops and arrays in the data step. The syntax in the data step is to specify a list of values numeric or character after the equal sign. Research on identifying loops has a long history, starting from 1970 when f. Sas program using character values for do loop youtube.
Rather, a sas array provides a different name to reference a group of variables. 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 generate data eliminate redundant code execute sas code conditionally. Avoid unnecessary loops in the sasiml language i have some advice on using do loops in sasiml language. Again, think of what a put statement doesit takes a sas value character or numeric, applies a format and writes out the result, usually to a file. That makes sas macro loops a powerful code generator tool allowing to produce multiple variations of sas code snippets with actually writing them just once. Purpose of do loops do loops process groups of sas statements repeatedly, reducing the number of statements required in repetitive calculations syntax of iterative do loops to construct an iterative do loop, specify an index variable and the conditions that will execute the loop. A quick intro to sas arrays and do loops gopinath narasimhan saskatchewan cancer agency march 12, 2014. A sas array is not a new data structure, the array name is not a variable, and arrays do not define additional variables.
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. Sas programming tutorials for beginners by priya sas online training for complete sas programming duration. The point is i have to use the last observations data to compute the lagged variable for the next observation. There are many variations of the do statement and these can be used in conjunction with arrays to accomplish a number of tasks that can otherwise be quite intractable. Each row is processed independent of others unless you explicitly keepretain data. As output, produce a table of illustrative test components, sorted by. Proc import combined with %do loop to read in the data from multiple excel worksheets. I have an excel workbook that i have assigned a libname and i would like to do formatting on the sheets which are labeled in a way that i thought would be conducive to set up a loop. Purpose of do loops do loops process groups of sas statements repeatedly, reducing the number of statements required in repetitive calculations. Pdf because one of the most powerful incentives to use the sas macro language.
Dread to get the member name and the scan function to extract the second. Some languages support a foreach loop that iterates over objects in a collection. There are two forms of conditional do loops, do until loops and do while loops. There are many variations of the do statement and these can be used in. Since the macro language is typically used to generate sas language code, you need to have a solid understanding of the sas language before you learn the macro language. Loops are fundamental to programming because they enable you to repeat a computation for various values of parameters. A sas macro to automate importing excel worksheets into sas. Compare the iteration with the do until and do while examples. These conditions include a start value for the index variable, a. We use this to extract the desired results from proc freq into three datasets. But you can use the % do loop in a macro like the following to accomplish this. Sep 07, 2011 avoid unnecessary loops in the sas iml language.
A comprehensive knowledge of the appropriate sas functions can often make the difference between a difficult and a fun programming task. Sas loops through rows automatically in a data step. Do until loops continue executing until the condition you have specified becomes true. Some of the documented functions may not work in the learning edition. Macro % do statements require integers for their start and stop values. Dates are handled as numbers with formats in sas r software. This paper presents a number of examples to demonstrate how to take advantage of the %do loop to build sas statements dynamically. 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 put function takes a sas value the first argument and writes out the formatted result using format supplied as the. Java project tutorial make login and register form step by step using netbeans and mysql database duration. The power of macros audrey yeo, aviva usa, west des moines, iowa abstract the sas macro facility is an extremely powerful tool that should be in the toolbox of every sas programmer. 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. Syntax of iterative do loops to construct an iterative do loop, specify an index variable and the conditions that will execute the loop.
635 465 147 768 31 206 332 813 881 1322 321 1370 267 1009 1191 1430 267 367 1226 951 982 1245 527 1217 212 834 282 642 1300 1267 587 390 980 935 543 609 524 1001 170 508 557 953 755 558