I've got a 2-D histogram (the plot is 3D - several histograms graphed side by side) that I've generated with the bar3 plot command. However, all the zero values show up as flat squares in the x-y plane. Is there a way I can prevent MATLAB from displaying the values? I already tried replacing all zeros with NaNs, but it didn't change anything about the plot. Here's the code I've been experimenting with:

x1=normrnd(50,15,100,1); %generate random data to test code
x2=normrnd(40,13,100,1);
x3=normrnd(65,12,100,1);

low=min([x1;x2;x3]);
high=max([x1;x2;x3]);
y=linspace(low,high,(high-low)/4); %establish consistent bins for histogram
z1=hist(x1,y);
z2=hist(x2,y);
z3=hist(x3,y);
z=[z1;z2;z3]';
bar3(z)

As you can see, there are quite a few zero values on the plot. Closing the figure and re-plotting after replacing zeros with NaNs seems to change nothing:

close
z(z==0)=NaN;
bar3(z)