BookmarkSubscribeRSS Feed
🔒 This topic is solved and locked. Need further help from the community? Please sign in and ask a new question.
Ajktulm
Calcite | Level 5

I have to a model

threshold = 100 -2*deltat + c1*sigma^a + c2*deltat^2 + c3*sigma^c * deltat^d

where I know 0<threshold<100 as it is in all my datapoints (https://pastebin.com/3pYiNFf1)

 

To do this I run the following code (and I am fully aware this approach is incredibly stupid/ridiculous but I can't think of anything better) using the nlmixed procedure with as model the binomial distribution with 100 trials, and succes chance hopefully threshold/100. 

 

PROC NLMIXED data=BEP;
PARMS c1=-1, c2=0, c3=0, a=1, b=1, c=1, d=1;
p = (100 - 2*deltat + c1*sigma**(a) + c2*deltat**(b) + c3*sigma**(c) * deltat**(d))/100;
model threshold ~ binomial(100,p);
run;

 

However when running this I get no output and the log says 

NOTE: Execution error for observation 1.
NOTE: The SAS System stopped processing this step because of errors.
 
Although I do get results if I remove the parameters a,b,c,d, I don't get any results when I include them.
 
This was run using SAS university edition version 3.8
1 ACCEPTED SOLUTION

Accepted Solutions
PGStats
Opal | Level 21

Run NLMIXED with option trace to get debug info. The problem is related to cases where sigma=0. NLMIXED is trying to take the log of sigma and fails. You can get convergence by replacing sigma=0 by sigma=0.01. 

 

With sigma=0.01, the results indicate that your model is overparameterized, likely because of the two terms involving sigma with different exponents. Just a guess.

PG

View solution in original post

1 REPLY 1
PGStats
Opal | Level 21

Run NLMIXED with option trace to get debug info. The problem is related to cases where sigma=0. NLMIXED is trying to take the log of sigma and fails. You can get convergence by replacing sigma=0 by sigma=0.01. 

 

With sigma=0.01, the results indicate that your model is overparameterized, likely because of the two terms involving sigma with different exponents. Just a guess.

PG

sas-innovate-2024.png

 

Secure your spot at the must-attend AI and analytics event of 2024: SAS Innovate 2024! Get ready for a jam-packed agenda featuring workshops, super demos, breakout sessions, roundtables, inspiring keynotes and incredible networking events.

 

Register by March 1 to snag the Early Bird rate of just $695! Don't miss out on this exclusive offer. 

 

Register now!

What is ANOVA?

ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.

Find more tutorials on the SAS Users YouTube channel.

Discussion stats
  • 1 reply
  • 302 views
  • 1 like
  • 2 in conversation