Error:Unexpected MATLAB expression.

Part o f a program I am writing goes as folows:

    if(y2(i)>y1(i)) 
                         ntra=ceil((y2(i)-y1(i))/h;
                         htra=(y2(i)-y1(i))/ntra; 
                         y=[y1(i):htra:y2(i)];
                         x=xtab(i);
                         ytabtra=eval(f);

The definition of f beeing:

temp=input('veuillez encoder la fonction principale f(x,y):','s');
    f= vectorize(temp);

I tested it with the input '3x+y'

When I programed this yesterday, everything worked, but when I tried again today I get:

??? Error: Unexpected MATLAB expression.

Error in ==> principal_1 at 45
                     ytabtra=eval(f);

Could anybody help me please?

Answer 1

[Image Analyst]

Well, what if "f"? You never assigned anything to it, so when it gets to eval(f) it doesn't know what f is. What were you intending? Are you sure that your code assigning f actually was run before you hit the eval statement? Set a breakpoint there to check and make sure f has some string value.

[Karel]

actually, it was a stupid oversight of my part: instead of entering 3*x+y, I entered 3x+y, which the program didn't recognise, Sorry to have botered you.