Using output of Proc Freq variables for input into Proc Format

Question

I want to grab the number of variable levels as well as the variable for the output of the unique identifiers but currently my method does not work. I want to then use the unique ID's and associate numbers 1-num_levels from proc freq.

Here is what I have for proc freq:

PROC FREQ DATA=my_data (keep=IDs) nlevels;
table all/out=out_data;
%let dim=levels;
%let IDs;
run;

Then I tried to use the macro variables but it didn't work so I am including the manual version of my proc format to give a good idea of what I am trying to achieve but hopefully trying to make it more automated.

PROC FORMAT; 
INVALUE INDEX
"1234" = 1
"2345" = 2
.
.
.
"8901" =25;
/*25 represents the output of the levels 
variable from proc freq but I couldn't figure out how to grab that either*/
RUN;

Any help would be appreciated. Thank you!

Answer 1

Here's a fully worked solution, that illustrates a the PROC FORMAT CNTLIN way of doing this. The idea here is to mask names with the observation number instead.

*Create list of unique names;
proc freq data=sashelp.class noprint;
    table name/out = mask;
run;

*create control data set. Variables that need to be set are:
   fmtname, start, label and type;

data name_fmt;
    set mask;
    fmtname = 'namefmt';
    type='J';

    *J specified character informat, C would be character format;
    start=name;
    label = put(_n_, z2.); *Use the row number as the recoded value;
run;

*create the format;
proc format cntlin=name_fmt;
run;

*Sample usage;
data class;
    set sashelp.class;
    name_masked = input(name, $namefmt.);
    drop name;
run;