Matlab: plotting frequency distribution with a curve

Question

I have to plot 10 frequency distributions on one graph. In order to keep things tidy, I would like to avoid making a histogram with bins and would prefer having lines that follo

Answer 1

How about interpolating with splines?

nbins = 10; %// number of bins for original histogram
n_interp = 500; %// number of values for interpolation
[counts, bins] = hist(data, nbins);
bins_interp = linspace(bins(1), bins(end), n_interp);
counts_interp = interp1(bins, counts, bins_interp, 'spline');
plot(bins, counts) %// original histogram
figure
plot(bins_interp, counts_interp) %// interpolated histogram

Example: let

data = randn(1,1e4);

Original histogram:

Interpolated:

Following your code, the y axis in the above figures gives the count, not the probability density. To get probability density you need to normalize:

normalization = 1/(bins(2)-bins(1))/sum(counts);
plot(bins, counts*normalization) %// original histogram
plot(bins_interp, counts_interp*normalization) %// interpolated histogram

Check: total area should be approximately 1:

>> trapz(bins_interp, counts_interp*normalization)
ans =
    1.0009