topic Re: Residuals in logistic regression in SAS Programming

Residuals in logistic regression

Walternate — Mon, 28 Jan 2013 15:43:59 GMT

Hello,

I have created a multiple logistic regression model and am trying to look at the residuals. The only process I have found (iplots) prints residuals for about 100 participants at a time, which is not ideal since I have over 5000 study subjects. Any help is much appreciated!

Thanks.

Re: Residuals in logistic regression

Reeza — Mon, 28 Jan 2013 16:02:07 GMT

Show your work/code please.

Re: Residuals in logistic regression

AncaTilea — Mon, 28 Jan 2013 16:13:09 GMT

How about

ODS GRAPHICS ON;

proc logistic data = your_data plots = (all);

model y = x;

run;

In my case, the plots are saved on the C:\Documents and Settings\User

Good luck,

Anca.

Re: Residuals in logistic regression

Walternate — Mon, 28 Jan 2013 16:14:35 GMT

proc logistic data=mydata;

class var1(reference=1) var2(reference=1) var3(reference=1);

model case(event='1')=var1 var2 var3/rsq ctable pprob=(0 to 1 by .1) lackfit risklimits iplots;

run;

Re: Residuals in logistic regression

Reeza — Mon, 28 Jan 2013 16:21:07 GMT

I think Anca solution is what you're looking for. In addition, I think you need to add the /param=ref option to your class statement.

Take a look at your output, specifically the Class level information and see if its what you want (basically your design matrix) or if you want the option I suggested.

Re: Residuals in logistic regression

AncaTilea — Mon, 28 Jan 2013 16:21:54 GMT

When I tried to run plots with Logistic with a data set that has more than 5000 observations I get this warning:

-------------

WARNING: Some plots have more than 5000 observations and are suppressed. Specify the

PLOTS(MAXPOINTS=NONE) option in the PROC LOGISTIC statement to display the plots.

Did you try this?

proc logistic data = my_data plots(maxpoints = none);

model...;

Re: Residuals in logistic regression

Walternate — Mon, 28 Jan 2013 16:28:11 GMT

Could you please explain what the /param=ref option is for?

Thanks!

Re: Residuals in logistic regression

AncaTilea — Mon, 28 Jan 2013 16:31:05 GMT

In your class statement you use 'reference = 1', which tells SAS that for the variable var1 the reference category is '1'.

You need the param = ref to tell SAS to use that reference coding in parameter estimates.

----

Re: Residuals in logistic regression

Reeza — Mon, 28 Jan 2013 16:31:51 GMT

It specifies how SAS creates the design matrix for class variables, the default is 'EFFECT CODING' when most people want 'REFERENCE CODING' instead.

SAS FAQ: In PROC LOGISTIC why aren't the coefficients consistent with the odds ratios?

Re: Residuals in logistic regression

Reeza — Mon, 28 Jan 2013 16:32:29 GMT

Not quite, it can still use that as the reference for Effect coding, but it won't be what you want necessarily.

Re: Residuals in logistic regression

AncaTilea — Mon, 28 Jan 2013 16:37:10 GMT

Thank you.