Basics of MATLAB - Basics of MATLAB and Beyond - page 50

NaN s by leaving them off the plot. For example, if we allow plot to try
to join the points with a straight line, the values on either side of the
NaN s terminate the line:

plot(y)
grid;box

If we calculate the difference between y -values, the results involving NaN s
are themselves NaN :

>> diff(y)
ans =
Columns 1 through 12
1 1 1 NaN NaN 1111111
Columns 13 through 19
1 NaN NaN 1 1 1 1

If we calculate the cumulative sum of y , everything from the first NaN
onwards is NaN :

>> cumsum(y)
ans =
Columns 1 through 12
1 3 6 10 NaN NaN NaN ... NaN
Columns 13 through 20
NaN NaN NaN NaN NaN NaN NaN NaN

matlab's surface plotting functions handle NaN s in a similar way:
z = peaks;
z(5:35,18:22) = NaN;
subplot(221)
plot(z')
subplot(222)
colormap(gray(64))
imagesc(z)
axis xy
subplot(223)
surfl(z)
shading flat
subplot(224)
contourf(z)