topic first difference data (selection) in SAS Procedures

first difference data (selection)

Golf — Tue, 21 Jul 2020 01:38:42 GMT

Hello,

I have the following data set.

city Year D87 X dx

1 82 0 a -

2 87 1 b (b-a)

3 82 0 c -

4 87 1 d (d-c)

5 82 0 e -

6 87 1 f (f-e)

What procedure should be used to achieve dx ?

Thank You

Re: first difference data (selection)

PGStats — Tue, 21 Jul 2020 02:01:07 GMT

In a data step:

pX = lag(X);
if D87 then dx = X - pX;
drop pX;

Re: first difference data (selection)

Golf — Tue, 21 Jul 2020 03:33:34 GMT

Thank You.

Re: first difference data (selection)

Golf — Tue, 21 Jul 2020 03:35:18 GMT

L_x = lag(x);
dx = x-L_x;
if d87 = 0 then dx = .;

Re: first difference data (selection)

mkeintz — Tue, 21 Jul 2020 03:45:34 GMT

Or you could use the DIF function, defined as X-lag(X):

dx=dif(x);

if d87=0 then dx=.;

Or slightly more economical.

dx= ifn(d87=1,dif(x),.) ;

Re: first difference data (selection)

Kurt_Bremser — Tue, 21 Jul 2020 10:59:40 GMT

Using the IFN() and DIF() functions, as suggested by @mkeintz, is the most economical way.

Re: first difference data (selection)

Golf — Tue, 21 Jul 2020 15:18:21 GMT

Thank you for your suggestion.
Best,

Re: first difference data (selection)

FreelanceReinh — Tue, 21 Jul 2020 20:03:08 GMT

Hello @Golf,

Glad to see that mkeintz's solution worked for you. Then it would be fair and help later readers if you marked his helpful reply as the accepted solution, not your own "thank you" post. Could you please change that? It's very easy: Select his post as the solution after clicking "Not the Solution" in the option menu (see icon below) of the current solution.