Creating histogram without using built in function

I am trying to create a code that mimics the hist() function but I am running into an issue on the final bin.

Here is what I have:

Pie=sin(2*pi*tt);                   %array of data p=sin(2*pi*t/T)  
L=10;                              %number of bins
minPie = min(Pie);                  %min value of array
maxPie = max(Pie);                  %max value of array
binwidth = (maxPie - minPie)/L;     %width of bin
binnum = 1+floor((Pie - minPie) / binwidth);    %value of array to a bin
bincounts = accumarray(binnum(:), 1);           %amount to each bin
X = minPie + (0:L) * binwidth;                  %X of histogram
figure (1)
bar(X, bincounts)                       %my histogram

figure (2)
hist(Pie,10)                        %matlab histogram

My code returns this figure which has 11 bins at a bin width of 0.2.

Matlab's hist function returns this figure which has 10 bins with a bin width of 0.2.

How can I change my last bin so that the two figures are identical?

[David Fariyike]

tt on the sin function is just equal spaced intervals (linspace) from an initial to a final time.

Answer 1

[Voss]

You're going to run into edge effects like that, due to the nature of floating-point arithmetic. You can just fix values out of bounds after calculating them.

tt = linspace(0,10,100);
Pie=sin(2*pi*tt);                   %array of data p=sin(2*pi*t/T)  
L=10;                              %number of bins
minPie = min(Pie);                  %min value of array
maxPie = max(Pie);                  %max value of array
binwidth = (maxPie - minPie)/L;     %width of bin

binnum = 1+floor((Pie - minPie) / binwidth);    %value of array to a bin
binnum(binnum < 1) = 1; % correct the edge effects
binnum(binnum > L) = L;

% bincounts = accumarray(binnum(:), 1);           %amount to each bin
bincounts = zeros(1,L);
for ii = 1:L
    bincounts(ii) = nnz(binnum == ii);
end

% use the bin centers for plotting:
X = minPie + (0.5:L-0.5) * binwidth;                  %X of histogram
figure (1)
bar(X, bincounts)                       %my histogram

figure (2)
hist(Pie,L)                        %matlab histogram