Matlab fplot: not enough input arguments

Question

I'm just starting to learn Matlab, and I've been searching around a lot for a solution.

Basically, I just need to fplot a function and then manipulate it more for later questions.

fplot(@(x) myfunc);

function y = myfunc(x)
    y = (x^3) - (4 .* x^2) - 1
end

Produces this error

Warning: Function behaves unexpectedly on array inputs. To improve performance,
properly vectorize your function to return an output with the same size and shape as
the input arguments. 
> In matlab.graphics.function.FunctionLine>getFunction
  In matlab.graphics.function.FunctionLine/updateFunction
  In matlab.graphics.function.FunctionLine/set.Function_I
  In matlab.graphics.function.FunctionLine/set.Function
  In matlab.graphics.function.FunctionLine
  In fplot>singleFplot (line 234)
  In fplot>@(f)singleFplot(cax,{f},limits,extraOpts,args) (line 193)
  In fplot>vectorizeFplot (line 193)
  In fplot (line 163)
  In HWA1_2 (line 1) 
Warning: Error updating FunctionLine.

 The following error was reported evaluating the function in FunctionLine update: Not
 enough input arguments.

It works when I just use fplot on its own.

fplot((x^3)-(4*x^2)-1)

If anyone could point out what I'm doing wrong I'd be very grateful. The reason I need it defined as a function is because I need to do more manipulations to it later on.

Mike Scannell · Accepted Answer · 2018-09-03 18:22:23Z

2

Your syntax for calling fplot is the problem, not your function. If you're passing a simple function handle, just use:

fplot(@myfunc)

The syntax you were using is how you'd create an anonymous function, but you forgot to include x in the equation. You could also write it like this and get the same result:

fplot(@(x) myfunc(x))

answered Sep 3, 2018 at 18:22

Mike Scannell

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