How to plot 3D surface plot for given x and y data? what is code for z?

{x = [1,2,3,77,5]; y = [22,13,2,4,5]; z = peaks(y); surf(x,y,z);}

In above code x stands for frequency and y stands for voltage, here I required 3 D surface plot representation where highest value of y axis forms peak at certain height represented by z axis. Hence, what is the correct code for z axis so that I will get surface representation of 2 D xy plot?