MATLAB: Change fminsearch() stepsize

fminsearchMATLABOptimization Toolboxstepsize

Dear Sir/Madam
I am trying to use fminsearch() function for certain optimization problem. I hope to change the intial step size of the function.
I tried the following code
 options = optimset('fminsearch');
 options.DiffMinChange=100;
 options.DiffMaxChange=200;
 [deltarR1, fmin1]=fminsearch(@XYZR_MeasureDefine,Deltar,options,XYZRcoodinate,BfieldData,NVBfield,[1,1,1]);
 %Deltar is the intial guess, Bfield Data, NVfield, [1,1,1] are other constant parameters
In principle , this 'options' should set the stepsize from 100 to 200. The stepsize actually does not change when I run the code.
Any suggestion?

Best Answer

fminsearch() does not use an initial step size. fminsearch() builds an initial simplex by taking taking the initial coordinates and systematically multiply one of them by 1.05, unless the coordinate was 0 in which case it uses 0.00025
DiffMinChange and DiffMaxChange are not optimset options(); they are optimoptions(), and opotimoptions is not used for fminsearch .
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