topic Re: create design matrix from long dataset in SAS Programming

create design matrix from long dataset

bootstrap_armada — Wed, 20 Sep 2017 16:15:18 GMT

I have a long dataset like the example below (in my real dataset I have thousands of ID's and approx one thousand distinct Dx values).

ID Dx

Pat1 A

Pat1 B

Pat1 C

Pat2 B

Pat2 D

Pat3 A

Pat3 D

And I want to generate a design matrix like the one below (obviously the real design matrix will be high dimensional with a column for each Dx value).

ID A B C D

Pat1 1 1 1 0

Pat2 0 1 0 1

Pat3 1 0 0 1

My original plan was to transpose the long dataset, and then let proc glm generate the design matrix using a class statement; however I can't get the data to transpose how proc glm would need it with distinct dx values in each dx column.

Using transpose I haven't been able to get anything better than the structure below.

ID Dx1 Dx2 Dx3

Pat1 A B C

Pat2 B D

Pat3 A

I've thought about approaches using loops, arrays, and proc sql, but I haven't been able to put the pieces together to get to the end design matrix I need.

Any help is appreciated, and while any answer that works is great, in my situation a proc sql solution would be optimal.

Thanks much!

Re: create design matrix from long dataset

Astounding — Wed, 20 Sep 2017 16:22:26 GMT

PROC TRANSPOSE can handle this. You just need to use this statement:

id Dx;

Since Dx is no longer going to be in the VAR statement, you may need to take a couple of additional steps (try it and see if they are needed):

Before transposing, create a variable that is 1 on each observation, and use that in the VAR statement of PROC TRANSPOSE.

After the transpose go back and replace missing values with zeros.

One final consideration ... your incoming data set may may be to deduplicated. You can't have multiple observations for the same ID with the same DX.

Re: create design matrix from long dataset

stat_sas — Wed, 20 Sep 2017 16:29:55 GMT

Hi,

Or if just need to generate a matrix.

proc tabulate data=have;
class id dx;
table id,dx=""*N="";
run;

Re: create design matrix from long dataset

bootstrap_armada — Thu, 21 Sep 2017 13:56:13 GMT

This is a good, simple solution - I hadn't thought of that approach with proc transpose. Thanks!