Why does my histogram become incorrect when I change the y-axis scaling to 'log'?

When I execute the following code:

hist(randn(100,1));

set(gca,'yscale','log')

the bars are incorrectly displayed; the histogram bars either become lines or disappear entirely.

Answer 1

[MathWorks Support Team]

The ability to create a log-scale histogram is not available in MATLAB. There are a couple of ways to work around this issue,

1. Change the underlying patch object vertices, as follows:

x = -5:0.1:5;

y = randn(100000,1);

hist(y,x);

%Workaround

% Get histogram patches

ph = get(gca,'children');

% Determine number of histogram patches

N_patches = length(ph);

for i = 1:N_patches

      % Get patch vertices

      vn = get(ph(i),'Vertices');

      % Adjust y location

      vn(:,2) = vn(:,2) + 1;

      % Reset data

      set(ph(i),'Vertices',vn)

end

% Change scale

set(gca,'yscale','log')

In this case, note that if the histogram only reports one instance of a value in one of its bins, then you will not see this value. This is because 1 (10^0) is the new baseline value for the y-axis.

2. Use SURFACE objects as shown below in an example:

x1 = [0 1];  y1 = [1 5];

x2 = [1 2];  y2 = [1 15];

x3 = [3 4];  y3 = [1 8];

surface('Xdata',x1,'Ydata',y1,'Zdata',zeros(2),'Cdata',ones(2)*.5)

surface('Xdata',x2,'Ydata',y2,'Zdata',zeros(2),'Cdata',ones(2)*.6)

surface('Xdata',x3,'Ydata',y3,'Zdata',zeros(2),'Cdata',ones(2)*.7)

set(gca,'yscale','log')

set(gca,'ylim',[0 100])

Note that if the boundaries of y include zero, then the surface objects are not drawn correctly since log(0) = -inf.