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8
Functions, Loops, Arrays, Macros

In this chapter, we study ways to make things more automated by using functions in R and Macro Language in SAS. In addition, we study loops (for and do) as well as arrays in SAS.

8.1 Functions

In R Functions in R are quite easy in Syntax. They are of the form:

FUNCTIONNAME+function(x,y,..parameters){ function description)

They are called by FUNCTIONNAME(input value)

In SAS we use Proc FMCP.

The FCMP procedures are used to write, compile, and test DATA step functions and CALL routines that can be used in DATA step. For more information, you can read http://support.sas.com/resources/papers/proceedings13/139‐2013.pdf

8.2 Loops

Loops are used for tasks that are repeatable. You can also use functions within iterations of loops. Note in SAS you need to use end to close loop and output to output data.

In SAS:

data ajay;
do i=1 to 10;
       Output;
end;
       run;

proc print data=ajay;
run;

Obs     i
1       1
2       2
3       3
4       4
5       5
6       6
7       7
8       8
9       9
10      10

data ajay2 (drop=i);
do i=1 to 10;
y=i**3+3**i+5;
       output;
       end;
       run;

proc print data=ajay2;
run;

Obs     y
1       9
2       22
3       59
4       150
5       373
6       950
7       2535
8       7078
9       20417
10      60054

In R:

> for (i in 1:10){print(i)}
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 6
[1] 7
[1] 8
[1] 9
[1] 10

> a1=function(x){x^3+3^x+5}

> for (i in 1:10){print(a1(i))}

[1] 9
[1] 22
[1] 59
[1] 150
[1] 373
[1] 950
[1] 2535
[1] 7078
[1] 20417
[1] 60054

8.3 Arrays

A SAS array is a way of creating a temporary group of variables for processing within a data step for repeatable operations. Arrays help simplify SAS code readability.

Example:

array balance[12] bal1-bal12;

Here array named balance has 12 variables from variable bal. 1 to bal. 12.

ARRAY months {12} $ 12 mth1-mth12 ('January' 'February' 'March' 'April' 'May' 'June' 'July' 'August' 'September' 'October' 'November' 'December');.

You can also use * within the number of variables [].

Here we use sashelp dataset pricedata and convert prices from USD to INR

data price ;
set sashelp.pricedata;

array price:inr{17} price:inr1-price:inr17;
array price:usd{17} price1-price17;

do i = 1 to 17;
price:inr{i} = price:usd{i}*70;
end;
run;

proc print data= price (obs=5);
var price:inr1-price:inr3 price1-price3;
run;


Obs  price:inr1   price:inr2   price:inr3   price1  price2   price3
1    3661.00      8050         2338.0       52.300  115      33.40
2    3661.00      8050         2338.0       52.300  115      33.40
3    3661.00      8050         2338.0       52.300  115      33.40
4    3661.00      8050         1987.3       52.300  115      28.39
5    3111.85      8050         2338.0       44.455  115      33.40

8.4 Macros

The Macro Language is a useful and unique tool within SAS language which helps to reduce SAS code, improve readability and pass data in an automated manner. It is composed of Macro variables and Macro Programs.

Let us take a basic Macro.

Symbolgen option Specifies whether the results of resolving macro variable references are written to the SAS log. That is useful for debugging especially if SAS Macro code shows an error at some part.

options symbolgen ;

Here we create a macro (named ajay) with one defined variable (i)

Note within the Macro i is referred by &i which denotes it is a macro variable

We use %mend to close the Macro

We then call the Macro using %macroname (here %ajay)

%macro ajay(i);

data new1;
do j= 1 to &i;
output;
end;
run;

proc print data=new1;
run;
%mend;

%ajay(5);

Let’s makes a global macro variable (outside the declared macro)

%let name='ajay';
options symbolgen ;
%macro ajay(i);

data new1;
newname=&name;
age=&i*&i;
run;

proc print data=new1;
run;
%mend;

%ajay(5);

Obs     newname     age
1       ajay        25

Or, we can dynamically assign dataset paths

%let pathfile = '/home/ajay4/book';
libname macro1 &pathfile;
run;

The SAS log shows the following

71    %let pathfile = '/home/ajay4/book';
72    libname macro1 &pathfile;
SYMBOLGEN: Macro variable PATHFILE resolves to '/home/ajay4/book'

NOTE: Libref MACRO1 was successfully assigned as follows:
   Engine: V9
   Physical Name: /home/ajay4/book
73    run;

We can use multiple words for %let. We can also &SYSDATE and &SYSDAY for todays date and day respectively

%let use = EngineSize Invoice MPG_City ;

title "Today's date is &SYSDATE9 and day is &SYSDAY";

proc means data=sashelp.cars mean;
var &use;
run;

Today's date is 12DEC2018 and day is Wednesday

The MEANS Procedure

Variable	Label	Mean
EngineSize Invoice MPG_City	Engine Size (L) MPG (City)	3.1967290 30 014.70 20.0607477

%PUT: This statement writes the text in SAS log.

%put &name;
%put &use;

From SAS Log

SYMBOLGEN: Macro variable NAME resolves to 'ajay'
70
71 %put &name;
'ajay'
72 %put &use;
SYMBOLGEN: Macro variable USE resolves to EngineSize
  Invoice MPG_City
EngineSize Invoice MPG_City

We can also do string operations using Macro variables.

%upcase: converts into upper case.
%substr: returns characters from specified position.
%scan: returns the variable whose number is specified.

options nosymbolgen;
%put &use;
%let newuse =%UPCASE(&use);
%put &newuse;

%let new2=%scan(&newuse,3);
%put &new2 ;

%let subword=%substr(&newuse, 3,5);
%put &subword;

71    options nosymbolgen;
72    %put &use;
EngineSize Invoice MPG_City

73    %let newuse =%UPCASE(&use);
74    %put &newuse;
ENGINESIZE INVOICE MPG_CITY

75
76    %let new2=%scan(&newuse,3);
77    %put &new2 ;
MPG_CITY

78
79    %let subword=%substr(&newuse, 3,5);
80    %put &subword;
GINES

Data _null_: To gain higher efficiency in a SAS program, creation of additional dataset can be avoided using this statement. It creates a null dataset.

CALL SYMPUT: This function assigns data step information to a macro variable. It has two parts:

This specifies a character expression that identifies the macro variable which is assigned a value. If the macro variable does not exist, the routine creates it.
This specifies a character constant, variable, or expression that contains the value that is assigned.

Here ODS helps create an output in an excel file while other macro variables help create the path for a file. Instead of proc. sort we can also put more elaborate analytical statements here.

%let pathfile = '/home/ajay4/book' ;
libname auto &pathfile;
run;
options compress=yes;
options symbolgen;
%macro impmth(mth,num);
data _null_ ;
/* call symput('unqxls',"'"||&pathfile||"unq"||&mth||'.xls'||"'" ); */
call symput('unqxls',"'"||'.xls'||"'" );
run;

proc sort data=auto.&num nodupkey;
by user_id;
run;

ODS HTML FILE=&unqxls;
proc print data=auto.#
run;
ODS HTML CLOSE;
%mend;

%impmth(01,issued)

8.5 Quiz Questions

How do we close a do loop in SAS?
How we get output in a do loop in SAS?
How do we create a function with two parameters in R?
How do we close a macro in SAS?
What command in data step helps create a null dataset?
How do I output macro variables in SAS log?
With which option do we print out macro variables in an SAS log?
Which function gives data step information to a macro variable?
Which function can be used to create output in excel format in SAS?
Which function can be used to create a global macro variable?

Quiz Answers

End
Output
function(x,y){commands}
%mend
Data _null_
%put
Symbolgen
Call symput
ODS HTML
%let

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