Array indices must be positive integers or logical values.

h=0.1;

x=a+h:h:b-h;

[Stefano Bernardi]

please how I can fix it?

Answer 1

[Image Analyst]

A thorough discussion is in the FAQ:

https://matlab.fandom.com/wiki/FAQ#.22Subscript_indices_must_either_be_real_positive_integers_or_logicals..22

Answer 2

[Stefano Bernardi]

[Stefano Bernardi]

now I change f in 1X9 but I have again the same problem

[Walter Roberson]

• you are constructing F and Fy to be functions that require three input variables (x, y, f) but you are only passing two inputs to them
• The equations you posted strongly suggest that P(x) is intended to mean that P is a function of x that should return a result that is the same length as x. P is a function, not an array.
• No comments are present as to what size F(x,y) needs to return, such as if x and y are different sizes.
• I would suggest to you that the f you use in F needs to be the same size as y, not a fixed size. Not unless you are willing to fix the size of y -- and in that case you should probably be passing in n or creating n... which would reflect into the size you create for P .
• You never vary x once you initialize it. Perhaps your P should be a function that ignores its input and returns a vector of length n-1 .
• Don't use inline().

%replace the *body* of esempio* with the following

    Pdata = [-20,-10,0,10,20,10,0,-10,-20];
    fdata = [2,3,4,5,6,5,4,3,2] .';
    
    P = @P9;
    F = @F9;
    Fy = @Fy9;
    
    a = 0;
    b = 1;
    alfa = 1;
    beta = 1;
    
    function Px = P9(x)       %vector result, orientation not important
      assert(numel(x) == numel(Pdata), 'x wrong size for P');
      Px = reshape(Pdata, size(x));
    end
    
    function Fxy = F9(x, y)   %column vector result!
      assert(numel(y) == numel(fdata), 'y wrong size for F');
      Fxy = fdata .* 2.* y(:);
    end
    
    function Fyxy = Fy9(x, y)  %column vector result!
      assert(numel(y) == numel(fdata), 'y wrong size for Fy');
      Fyxy = fdata .* 2;
    end

 end    %this END is important!

It is important that P9, F9, Fy9 are nested functions within the esempio* function, not independent functions. They must be nested, in order to access the Pdata and fdata arrays.