How can I peform same datastep across many variables in SAS? - sas

Question

I have data that looks like this and has 500 variables with a target:
var1 var2 var3 var4 ... var500 target
The names of the variables are not sequential as above so I don't think I can use something like var1:var500. I want to loop through the variables to create graphs. Some of the variables are continous and some are nominal.
for var1 through var500
if nominal then create graphtypeA var[i] * target
else if continous then create graphtypeB var[i] * target
end;
I can easily create a second table that has the data type in it to check against. Arrays seem like they might be useful to peform this task of looping through variables. Something like:
data work.mydata;
set archive.mydata;
array myarray{501] myarray1 - myarray501
do i=1 to 500;
proc sgpanel;
panelby myarray[501];
histogram myarray[i];
end;
run;
This doesn't work though and it doens't check to see what type of variable it is. If we assume I have another sas.dataset that has varname and vartype (continuous, nominal) how can I loop through to create the desired graphs for the given vartype? Thanks in advance.

Answer 1

Basically, you need to loop over some variables, apply some logic to determine the variable type, then produce output depending on the variable type. While there are many approaches to this problem, one solution is to select your variables into a macro variable, loop over this "list" (not a formal data structure) of variables, and use macro control logic to designate different subroutines for numeric and character variables.
I'll use the sashelp.cars data set to illustrate. In this example the variable origin is your 'Target' variable and the variables Make, Type, Horsepower, and Cylinders are the numeric and character variables.
* get some data;
data set1 (keep = Make Type Origin Horsepower Cylinders);
set sashelp.cars;
run;
* create dataset of variable names and types;
proc contents data = set1
out = vars
noprint;
run;
* get variable names and variable types (1=numeric, 2=character)
* into two macro variable "lists" where each entry is seperated
* by a space;
proc sql noprint;
select name, type
into :varname separated by ' ', :vartype separated by ' '
from vars
where name <> "Make";
quit;
* put the macro variables to the log to confirm they are what
* you expect
%put &varname;
%put &vartype;
Now, use a macro to loop over the values in the macro variable list. The countw function counts the number of variables, and uses this number as the loop iterator limit. The scan function reads in each variable name and type by its relative position in the respective macro variable lists. For each variable the type is then evaluated and a plot is produced depending on whether it is character or numeric. In this example, a histogram with density plot is produced for numeric variables and a bar chart of frequency counts is produced for character variables.
The loop logic is general, and Proc sgpanel and Proc sgplot cab be modified or replaced with other desired data step processing or procedures.
* turn on options that are useful for
* macro debugging, turn them off
* when using in production;
options mlogic mprint symbolgen;
%macro plotter;
%do i = 1 %to %sysfunc(countw(&varname));
%let nextvar = %scan(&varname, &i, %str( ));
%let nextvartype = %scan(&vartype, &i, %str( ));
%if &nextvartype. = 1 %then %do;
proc sgpanel data=set1 noautolegend;
title "&nextvar. Distribution";
panelby Origin;
histogram &nextvar.;
density &nextvar.;
run;
%end;
%if &nextvartype. = 2 %then %do;
proc sgplot data=set1;
title "&nextvar. Count by Origin";
vbar &nextvar. /group= origin;
run;
%end;
%end;
%mend plotter;
*call the macro;
%plotter;

Answer 2

Unfortunately it is not possible to use arrays outside a data step in the way that you propose here, at least not in any very efficient way. However, there are quite a few options available to you. One would be just to call your graphing proc once and tell it to graph every numeric variable in your dataset, e.g. like so:
proc univariate data = sashelp.class;
var _NUMERIC_;
histogram;
run;
If the variables you want to graph that are of the same type are adjacent in the column order of your dataset, you can use a double-dash list, e.g.
proc univariate data = sashelp.class;
var age--weight;
histogram;
run;
In general you should seek to avoid calling procs or running data steps separately for every variable - it is nearly always more efficient to call them just once and process everything in one go.