MATLAB: Problem with built in and interp1

builtininterp1MATLAB

All, I'm having an issue that built in cant find the native interp1 function, see code below:
   % initialsie
   x = [0:0.1:2*pi];
   % run a check on syntax and method:
   default = sin ( x );
   check = builtin ( 'sin', x ); 
   % is it equal? It should be:
   isequal ( default, check )
   % now I try the same for interp1
   default2 = interp1 ( x, check , pi/2 )
   % try the same with the builtin command:
   check2 = builtin ( 'interp1', x, check, pi/2 ); 
   ??? Error using ==> builtin
   Cannot find builtin function 'interp1'
Computer details: Windows XP – r2010b
Is this expected behaviour? Is it repeated on other versions/platforms?
I have interp1 overloaded – because the inbuilt interp1 has poor error messages – but I want to be able to run the built in one to verify that the results of the two are the same (automated testing), the only way I can think to do it other than built in is to remove the path to the overloaded one – but it would mean a lot of rmpath, addpath etc…. So I'd like a neater solution…
Thanks

Best Answer

interp1 is not a built-in function, but an M-file. Therefore you observe the expected and wanted behaviour.
See:
which interp1 -all
which sin -all
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