Programming the statistical procedures from SAS

Error: QUANEW needs more than 200 iterations

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Posts: 18

Error: QUANEW needs more than 200 iterations

I am using NLMIXED for Negative Binomial modeling with user defined functions. One of the models worked, but when I replaced a function from :

 mu= 5*365*((MINAADT)**beta_1)* ((MAXAADT)**beta_2)*(EXP(beta_0))

with  this:

 5*365*(beta_0 + beta_1/((1+beta_2 *(MINAADT)**beta_3)*(1+beta_4*(MAXAADT)**beta_5)));

 Following error is shown in the Log.


 ERROR: QUANEW Optimization cannot be completed.
NOTE: QUANEW needs more than 200 iterations or 2000 function calls.
NOTE: PROCEDURE NLMIXED used (Total process time):
real time 0.19 seconds
cpu time 0.12 seconds

Posts: 4,241

Re: Error: QUANEW needs more than 200 iterations

You didn't ask a question, but 

1. If you are asking why the model didn't converge, the most likely reason is that the model does not fit the data and/or you did not provide a good initial guess for the parameters.

2. If you are asking what to do about it, then

   2a. Make a better initial guess for parameters

   2b. Change to a different optimize, such as  TECH=NMSIMP or TECH=NRRIDG

   2c.If you believe the model is almost converging, you can increase the number of iterations and the number of function evaluations that are permitted: MAXITER=500 MAXFUNC3000.

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