Dear All.
I am fitting some function at data for range 2 to 200, but it failed. When i change the range to 2 to 108 it gives me nice fitting. But just after 108 the functions fails to fit with message “Abnormal termination of minimization” .
So i tried to understand the output and reason for this, what i found is
- till range 108 function is fitting nice with status:
FCN=62.2591 FROM MIGRAD STATUS=CONVERGED 313 CALLS 314 TOTAL
EDM=8.22293e-09 STRATEGY= 1 ERROR MATRIX ACCURATE
EXT PARAMETER STEP FIRST
NO. NAME VALUE ERROR SIZE DERIVATIVE
1 c 9.63910e+02 1.76001e+01 2.16986e-02 -1.14205e-05
**2 q 1.35079e+00 3.94012e-02 9.05930e-02 5.74516e-07**
3 k 1.34253e+00 3.95433e-02 2.60646e-05 6.40928e-03
4 nV 5.51199e+00 1.23216e-01 5.47718e-05 -3.20463e-03
5 nV0 1.15495e-01 2.67276e-01 3.67715e-03 4.71362e-05
So looking closely at this output i found the First derivative of 2nd parameter is very small e-07.
- when i fit the data for full range 2 to 120 it gives me output as
FCN=6.3077e+306 FROM MIGRAD STATUS=FAILED 284 CALLS 285 TOTAL
EDM=inf STRATEGY= 1 ERROR MATRIX UNCERTAINTY 100.0 per cent
EXT PARAMETER APPROXIMATE STEP FIRST
NO. NAME VALUE ERROR SIZE DERIVATIVE
1 c 1.00000e+00 1.41421e+00 -0.00000e+00 0.00000e+00
2 q 1.32690e+00 3.57038e-02 -0.00000e+00 0.00000e+00
3 k 2.50000e+01 1.74468e-152 -0.00000e+00 1.52685e+305
4 nV 6.00000e+00 1.41421e+00 -0.00000e+00 0.00000e+00
5 nV0 2.80000e-01 2.46491e-01 -0.00000e+00 0.00000e+00
So it is clear that step size and its derivative is playing role in this failure and success of function.
Could some one please elaborate it more that how this works or any document/info available on this from which i can read and understand the reason better
Thanks and Regards
Sandeep