"Struct contents reference from a non-struct array object" error in fzero

A bit of background: I have a few versions of Matlab on my computer (2012a and 2014a). I recently started having problems with commands that used to work, an example being fzero. When I run it, I get the error "Struct contents reference from a non-struct array object." Strangely, this happens both on my primary version (2014a) and backup version (2012a). I also installed 2016a to test it and it's also giving the same error.

>> X = fzero(@(x) sin(3*x),2)
Struct contents reference from a non-struct array object.

Error in fzero (line 167)
    error(message(errStruct.identifier));

Does anyone have any idea what's going on or how to fix this?

[Adam]

What does

which -all sin

show?

Answer 1

[Steven Lord]

Make sure you're calling the version of the fzero function included in the release of MATLAB that you're using.

which -all fzero

Also make sure you haven't overloaded the fcnchk function.

which -all fcnchk

[Shlomo]

I had overloaded fcnchk, thanks!

Answer 2

[Jan]

You can set a breakpoint in the "[FunFcn,errStruct] = fcnchk(..." line of fzero (should be line ~165 - I have another Matlab version). Then step into fcnchk and check, what's going on there. It this the function inside the folder \funfun\ ?

If not, it is most likely a user-defined function (as Steven has mentioned before). Avoid shadowing built-in function and add user-defined paths at the bottom of the Matlab path only. See http://de.mathworks.com/matlabcentral/fileexchange/27861-uniquefuncnames for a tool to identify user-defined functions, which accidently shadow builtin functions.