topic Assign Matrix Name via DO Loop Function in SAS/IML Software and Matrix Computations

Assign Matrix Name via DO Loop Function

MarkGIP — Sun, 20 Nov 2011 20:32:59 GMT

Hi! It's me again....

While working with the DO loop function I encountered another problem;) I'd like to create several matrices with the help of the DO loop function but I'm still struggling with the matrices' names. Is it possible to assign a matrix name via the DO loop function as well?

Example:

do i=1 to 10;

Matrix_i=.....

end;

Thank you for your help!

Re: Assign Matrix Name via DO Loop Function

MarkGIP — Sun, 20 Nov 2011 21:25:23 GMT

Oh... nevermind. I just discovered the article of Rick on this topic..... Thank you Rick;)

But maybe somebody knows how to address a specific matrix with the DO Loop Function.

Example:

the functions are as follows:

m1=x1

m2=x2-x1

...

m10=x10-x9

Thank you....

Re: Assign Matrix Name via DO Loop Function

Rick_SAS — Mon, 21 Nov 2011 14:58:10 GMT

It is very rare that you need to have matrices of different names (as I explain in the article prior to the one you reference).

Sometimes people THINK they need to do this because they are trying to wrap SAS/IML statements within a macro loop, which is rarely necessary. Instead, you can use the SAS/IML language itself to perform whatever the macro loop is doing.

You didn't post an example, but one common programming technique is to have all of the x vars in an nx10 matrix, where each column is a variable.

Then the following statements form a matrix m where each column is what you want:

y = j(n,1,0) || x; /* temp: append column of zeros */

m = y[,2:11] - y[,1:10];

free y;

Another alternative, if you don't need the whole matrix, is to loop:

do i = 1 to 10;

if i = 1 then m=x[,i];

else m = x[,i] - x[,i-1];

/* do something with m, which is m_i in your notation */

end;