Frequency Counts of Distinct Variables

[acros]

Using a list of procedures, I would like to find the number of patients seen each month. I have data that looks like this:

Patient       Procedure Type        Month Procedure Occured

A               Mammogram            Jan

A               CBE                        Feb

B               Mammogram            March

C               Mammogram            Jan

C               CBE                        Jan

C               Ultrasound               Feb

What would be the simplest way to get the number of distinct patients seen each month. I want to get this output:

Month     Number of Distinct Patients

Jan                2                                      [Patient A and C]

Feb                2                                      [Patient A and C]

March            1                                        [Patient B]

[art297]

proc sql would be one of many ways:

proc sql;

  create table want as

    select Month_Procedure_Occured as month,

           count(distinct patient) as Number_of_Distinct_Patients

      from have

        group by Month_Procedure_Occured

  ;

quit;

[acros]

Awesome! Thank you, Arthur!