Hi,
When this error occurs, additional information is typically written to the output file generated by PROC ARIMA. If you see the following message in the PROC ARIMA output:
The estimation algorithm did not converge after 50 iterations.
then add the MAXITER= option to the ESTIMATE statement and increase the number of iterations from the default of 50 to a larger number, such as 250. For example:
estimate p=5 q=4 maxiter=250;
If the model failed to converge in fewer than 50 iterations, then you might need to try specifying:
- a different estimation method, such as METHOD=ML,
- different starting values for the model parameter estimates (See Details > Initial Values section of PROC ARIMA doc), or
- a different model.
If this information does not allow you to correct the error, then please provide any additional messages written to the output file or the "ARIMA Estimation Optimization Summary" table, which should be displayed in the output.
I hope this helps!
DW