Utility Bugs: region-projection

Bugs

1. PROJECTION and REGION-PROJECTION do not recognize the parameters by number.

2. Region-projection fails with "Error: The LM alpha matrix is null."

Bugs

1. PROJECTION and REGION-PROJECTION do not recognize the parameters by number.

   They must be specified as model_name.param_name, not model_name.param_number (e.g. PROJECTION poly.c0 vs PROJECTION poly.1).

2. Region-projection fails with "Error: The LM alpha matrix is null."

   sherpa> region-projection model.param2 model.param3
   Region-Projection: computing grid size with covariance...done.
   Error: The LM alpha matrix is null.
     --   ==> bad parameter value choices.
   

   One cause is parameter step size at parameter bounds. For instance, the default step size for a Gaussian fwhm is 0.01 times the current value; if the value hits its hard minimum (approximately 10^-38) during projection, then the step size will not be large enough to cause the statistic to change, leading to a null alpha matrix.

   Workaround:

   S-Lang could be used to avoid this problem:

   sherpa> tryone=run_regproj(["model.param2","model.param3"])
   sherpa> print(tryone)
   NULL
   

   If NULL, then change the optimization method to powell and try again:

   sherpa> () = sherpa_eval("method powell")
   sherpa> sherpa.regproj.fast = 0
   
   sherpa> trytwo=run_regproj(["model.param2","model.param3"])
   done.
                      outer grid loop 20% done...
                      outer grid loop 40% done...
                      outer grid loop 60% done...
                      outer grid loop 80% done...
   Minimum: 0.0707442
   Levels are: 2.36674 6.25174 11.9007
   
   sherpa> print(trytwo)
   x0               =  Double_Type[100]
   x1               =  Double_Type[100]
   y                =  Double_Type[100]
   levels           =  Double_Type[3]
   name             =  String_Type[2]
   bfit             =  Double_Type[2]
   config           =  sherpa_VisParEst_State
   

   Then change the method back to LM, if desired.