Technology Tales

Creating a data-driven informat in SAS

27^th September 2019

Recently, I needed to create some example data with an extra numeric identifier variable that would be assigned according to the value of a character identifier variable. Not wanting to add another dataset merge or join to the code, I decided to create an informat from data. Initially, I looked into creating a format instead, but it did not accomplish what I wanted to do.

data patient;
    keep fmtname start end label type;
    set test.dm;
    by subject;
    fmtname="PATIENT";
    start=subject;
    end=start;
    label=patient;
    type="I";
run;

The input data needed a little processing as shown above. The format name was defined in the variable FMTNAME and the TYPE variable was assigned a value of I to make this a numeric informat; to make character equivalent, a value of J was assigned. The START and END variables declare the value range associated with the value of the LABEL variable that would become the actual value of the numeric identifier variable. The variable names are fixed because the next step will not work with different ones.

proc format lib=work cntlin=patient;
run;
quit;

To create the actual informat, the dataset is read by the FORMAT procedure with the CNTLIN parameter specifying the name of the input dataset and LIB defining the library where the format catalogue is stored. When this in complete, the informat is available for use with an input function as shown in the code excerpt below.

data ae1;
    set ae;
    patient=input(subject,patient.);
run;