You have to give fminsearch a function of one parameter vector. I created two versions of your ‘fun’ function, one to use as an argument to fminsearch and one for the plot, vectorising both functions so they will work:
% MAPPING: b(1) = x, b(2) = y
fun=@(b)100*(b(2)-b(1).^2).^2+(1-b(1)).^2; % Argument To ‘fminsearch’
[z,val]=fminsearch(fun,[3,3])
x=-10:1:10;
y=-10:1:10;
[X,Y] = meshgrid(x,y); % Create Matrix Arguments
funplot=@(x,y)100*(y-x^2)^2+(1-x)^2; % Plotting Version
figure(1)
surfc(X, Y, funplot(X,Y))
grid on
I could have used the same function for both, but this is more straightforward.
