How to do surf plot if Z is not a matrix?

I'm trying to make a 3-D surf plot but I'm not sure how I can acquire the Z value, because a is not defined and when I try to plug in numbers for a, and try to surf plot it, it says Z is not a matrix.

f(X,Y) = Z = 0.2 + sin(2*π*a*x)/(2*π*x) + sin(2*π*a*y)/(2*π*y)

HINT: Use the following code to set the range of x and y.

x=[-5:0.2:5]+eps; y=x; [X,Y]=meshgrid(x,y)

how can I make Z a matrix so I can use surf(X,Y,Z)

Answer 1

[Marta Salas]

Let's assume a is a number. There is a value of Z for every (X,Y), thus, Z is a matrix and it has same size as X.

a = 1; 
x=[-5:0.2:5]+eps; 
y=x; 
[X,Y]=meshgrid(x,y)

Z = 0.2 + sin(2*pi*a*X)./(2*pi*X) + sin(2*pi*a*Y)./(2*pi*Y); 

figure, surf(X,Y,Z)

[Youssef Khmou]

hi, i agree, this is an efficient way rather than using x,y loops .