Regarding first.(variable) and last.(variable)

[Wken1122]

Hi,
Can someone explain what does this mean?

FIRST_REGNUMBER=FIRST.REGNUMBER ;
LAST_REGNUMBER=LAST.REGNUMBER;

I had tried to read the explanation from different source but I am still confuse.

Thank you.

[Criptic]

It gives you the first/last row of a group. A quick example:

data aa1;
    set sashelp.cars;
    by make;

    if first.make then
        output;
    else if last.make then
        output;
run;

Gives you a table with only the first and last row per make in the table

[RW9 · Accepted solution]

A temporary flag is added to the data, called first.<variable> and last.<variable> for each variable in the by group, this flag can then be used to determine if the record is the first or last occurence within the by group.

There are many guidance documents out there about this:

https://onlinecourses.science.psu.edu/stat481/node/9

For example.

Also, as a tip, do not code all in uppercase.

[Kurt_Bremser]

Since the automatic first. and last. variables (which are created when a by statement is present in the data step) are not included in any output data, these assignments are a technique to make the values visible in the output dataset.