Here is one way, I'll use Data as the residuals
Data = randn(1000,1); %just making up some junk data
binWidth = 0.7; %This is the bin width, you have to decide what makes sense
% for you
binCtrs = -3:0.7:3; %Bin centers, same thing, it depends on your data
n=length(Data);
counts = hist(Data,binCtrs);
prob = counts / (n * binWidth);
H = bar(binCtrs,prob,'hist');
set(H,'facecolor',[0.5 0.5 0.5]);
% get the N(0,1) pdf on a finer grid
hold on;
x = -3:.1:3;
y = normpdf(x,0,1); %requires Statistics toolbox
plot(x,y,'k','linewidth',2);
