topic Re: Box-cox proc transreg in Statistical Procedures

Box-cox proc transreg

uzma03505621 — Thu, 03 Jun 2021 19:11:40 GMT

I am using Proc transreg to identify which link function will be appropriate for my dependent variable in the GLM model. I used the code as follows:

proc transreg data=finalfile;
model boxcox(cost/lambda=-1 to 2 by .5)=identity(&variablelist);
run;

I get an error
ERROR: 24 invalid values were encountered while attempting to transform variable cost. Is it because my dependent variable has 24 observations with zero costs.

How can I resolve this issue

As I changed the code by adding parameter=1

It works giving me the following output and that lamba=0 is selected

The TRANSREG Procedure

TRANSREG Univariate Algorithm Iteration History for BoxCox(cost)
Iteration Number	Average Change	Maximum Change	R-Square	Criterion Change	Note
1	0.00000	0.00000	0.15025		Converged

Algorithm converged.

Please assist me with right method. Thank you

Re: Box-cox proc transreg

jiltao — Thu, 03 Jun 2021 19:16:47 GMT

Your Lambda list includes 0, which is the log transformation. Log of 0 is undefined, and that is why you received that error message.

You might want to exclude these observations, at least for lambda=0.

Re: Box-cox proc transreg

WarrenKuhfeld — Thu, 03 Jun 2021 19:43:34 GMT

https://documentation.sas.com/doc/en/pgmsascdc/9.4_3.4/statug/statug_transreg_details02.htm

As you figured out, you can specify PARAMETER= to add a value to each datum to avoid log 0 and other invalid operations. There are many other ways to get nonlinear transformations in TRANSREG and other procedures.