MATLAB: Str2num strange behaviour

documentedevalstr2doublestr2num

Dear, I have this code:
svmKernel ={'rbf','gaussian', 'linear','2','3','4'};
for k=1:numel(svmKernel)
    [p, status] = str2num(svmKernel{k});
    if ~status; t = templateSVM('Standardize',true,'KernelFunction',svmKernel{indK});                    
    else; t = templateSVM('Standardize',true,'KernelFunction','polynomial', 'PolynomialOrder', p); end
WHY str2num returns p = 
    Linear Function:
    Parameters: [1×1 struct]
and status = 1 when issuing [p,status] = str2num('linear')?
   [p, status] = str2num('linear')
Linear Function:
    Parameters: [1×1 struct]
status =
  logical
   1

Best Answer

"str2num strange behaviour"
It is not strange behavior at all: str2num (unfortunately) relies on eval, as the str2num help clearly states "...str2num uses the eval function, which can cause unintended side effects when the input includes a function name." You provided str2num a function name to evaluate... you can easily find out which function it is evaluating:
which linear -all
As the str2num documentation recommends, you could avoid the whole problem simply by using str2double (which could be called before the loop), then using isnan.
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