I need to define 2 variables and random sample from these.

KMaxwell — Tue, 11 Oct 2022 02:14:19 GMT

I want to create varX = (w, b, h, s) [4 cardinal variables] and varY = (yes, no) and then sample with replacement, with probability. ProbX = (0.6, 0.2, 0.15, 0.05) and ProbY = (0.8, 0.2). The sample size for X is X_total = (20, 50, 100, 200, 500 and 1000) and sample size for Y is each type of X for any given X_total and I have to do this by bootstrap and then compare them against the theoretical results of a 2D chi-square test. I am stuck at defining the variables X and Y. Can someone please help me with the syntax or point me to a tutorial on how to define variables in SAS? I'm familiar with R and have no clue on this one.

Thanks

Re: I need to define 2 variables and random sample from these.

ballardw — Tue, 11 Oct 2022 21:31:26 GMT

I don't understand some of your question because you are mixing "variable" with "value" , I think.

Without any other values involved one basic approach to making a data set with a fixed number of observations would look like this:

data yournamegoeshere;
   do i = 1 to 100;
       output;
   end;
run;

That will create as sequence of records with the value of the variable i = 1,2,3 ... 100, which you may see are the limits of the do loop starting at 1 ending at 100.

The Rand('table') function is the way to provide given probabilities to selecting values. I'll show the second as it has a useful bit of SAS information for use:

data example;
  do i= 1 to 10;
     y= rand('table',.2,.8)-1;
     output;
  end;
run;

The table function will assign the value 1 with the first probability, 2 with second, 3rd etc. If your total of the probabilities provided totals less than 1 then then the remaining chance will go to N+1. If the total of the probabilities exceeds 1 this gets a bit harder to explain so leave it as best to have the parameters total to 1.

The above is my suggestion to create a variable that is coded 0/1 with 1 standing for Yes(or True). SAS will will treat the value 1 as True and 0 as False so you can simplify some code involving IF constructs to "If Y then <do something>". If you use Y/N or 'Yes/No' or similar then you have to explicitly state the value in comparisons. Additionally summary counts for a 1/0 coded variable can be accomplished with the SUM function, the sum is the number of 1's and the Mean is the percent of 1's as a decimal value.

The 4 level would look like:

data example;
  do i= 1 to 100;
     y= rand('table',.2,.9)-1;
     x= rand('table',0.6, 0.2, 0.15, 0.05) ;
     output;
  end;
run;

Which will generate X of 1,2,3 or 4. If you want to SEE something like w, b, h, s then create a custom format and use that when you need to see those values.

Proc format;
value myx
1='w'
2='b'
3='h'
4='s'
;
run;

proc freq data=example;
   format x myx. ;
run;

Formats are the basic way of controlling displayed values in SAS. They have an additional functionality that groups defined by a format will be used for reporting, analysis and most graphing tasks. So in your example if we created a format like

Proc format;
value myxbh
1='w'
2,3='bh'
4='s'
;
run;

We could

Proc freq data=example;
    format x myxbh. ;
run;

see the affects of having that 'bh' appear with roughly .35 probability without having to recreate the data set.

Note: do not end the name of a format with a digit. The digits in formats control display positions so myx3. would occupy 3 output positions in general (even when only 1 is used padded) .

Part of what I have no clue of is this: The sample size for X is X_total = (20, 50, 100, 200, 500 and 1000). IS implies a single value to me. My guess is that in SAS you either create multiple data sets by changing the upper limit of i in the examples OR create one data set with 1000 records and then filter the data set for use by using a Where statement to restrict which records are used for a given purpose. A third approach could be to use a format on the I variable.

data example;
  do i= 1 to 1000;
     y= rand('table',.2,.9)-1;
     x= rand('table',0.6, 0.2, 0.15, 0.05) ;
     output;
  end;
run; 

Proc format;
value myx
1='w'
2,3='bh'
4='s'
;
value i_20_
1 - 20 = 'first 20'
other='More than 20'
;
value yn
0='N'
1='Y'
;
run;

proc freq data=example;
   by i;
   table x*y /chisq;
   format i i_20_. x myx. y yn.;
run;
/* or */
Proc freq data=example;
   where i le 20;
   table x*y /chisq;
   format i i_20_. x myx. y yn.;
run;

Re: I need to define 2 variables and random sample from these.

Rick_SAS — Wed, 12 Oct 2022 10:38:55 GMT

If you want to simulate two independent discrete variables (uncorrelated), you can use the RAND function and the "Table" distribution. See

https://blogs.sas.com/content/iml/2011/07/13/simulate-categorical-data-in-sas.html

That article has a macro variable

%let NSim = 10000;  /* sample size. 20, 50, 100, 200, 500 and 1000 */

that determines the sample size.

I don't understand the rest of your questions. Since you are "familiar with R," you can post your R program and maybe that will help us understand what analysis you are attempting.

topic I need to define 2 variables and random sample from these. in SAS Programming

I need to define 2 variables and random sample from these.

Re: I need to define 2 variables and random sample from these.

Re: I need to define 2 variables and random sample from these.