input=f(x) or f(x,y) how to plot/surf such unknown funktions?

i am planning to write a program which is able to plot/surf an inserted function input=f(x,y)

i want to use it just to make those functions visable in 2d/3d for my maths class so my questions are:

how to get an function into matlab?

and how to plot/surf that unknown function?

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ich möchte ein programm schreiben dass es mir ermöglicht mathematische funktionen (f(x,y) einzulesen und diese optisch auf dem bildschirm ausgibt um sie besser im unterricht besprechen zu können (erweiterungen des programmes werden dann ggf nullstellen berechnung etc)

Answer 1

[Wayne King]

   [X,Y] = meshgrid(-2:.2:2, -4:.4:4);
   Z = X .* exp(-X.^2 - Y.^2);
   surf(X,Y,Z)

Then you might want to shade

shading('interp');

or

    shading('flat');

[Markus Doll]

thx so far.

but how to get z=input(f(x,y));? like f(x,y)=cosd(x)-sind(y)?

[Markus Doll]

i dont want to change its colour

i want to know how to insert a function by hand

Z = ((((X .* exp(-X.^2 - Y.^2))));

in way that z= a new inserted funktion every time like x²+y or y²+x^4-2*xy or....

Answer 2

[Wayne King]

If you like Andrei's suggestion

z = eval(['@(x,y)',input('f(x,y) = ','s')])

Then user enters:

cosd(x)-sind(y)

ezmesh(z)

[Markus Doll]

ok now i see that this idea "hey let's write a program to show all funktions inserted!"is getting pretty hard for someone who just startet with it^^

thx by now

i'll try to get it rdy for use.