Your code appears to use a variable "score" without defining it.
You can create the histogram by calculating it yourself as you are trying to do, or using the hist function
n = 1000;
x = randn(n,1);
[heights,locations] = hist(x);
But if you want something comparable to a probability density, you need to modify the histogram to have area 1 (or scale up the density instead):
width = locations(2)-locations(1);
heights = heights / (n*width);
bar(locations,heights,'hist')
Now you can superimpose a density such as the standard normal density:
grid = linspace(min(x),max(x));
line(grid,exp(-.5*grid.^2)/sqrt(2*pi),'color','r')
If you have the Statistics Toolbox, you could use normpdf to calculate the density.
