Spatial Data - MATLAB Recipes for Earth Sciences - page 275

Fig. 7.10 Two-dimensional plot of a point distribution. h e distribution of objects in the i eld
is tested for uniform distribution using the ˇ2-test. h e xy data are organized into 25 classes
that are subareas with dimensions of 2-by-2.
hold off
A three-dimensional version of a histogram hist3 is used to display the
spatial data, organized in classes (Fig. 7.11).
hist3(data,[5 5]), view(30,70)
As with the equivalent two-dimensional function, the function hist3 can be
used to compute the frequency distribution n_obs of the data.
n_obs = hist3(data,[5 5]);
n_obs = n_obs(:);
For a uniform distribution, the theoretical frequencies for the dif erent
classes are identical. h e expected number of objects in each square area
is the size of the total area 10∙10=100 divided by the 25 subareas or classes,
which comes to four. To compare the theoretical frequency distribution with
the actual spatial distribution of objects, we generate a 5-by-5 array with an
identical number of objects.
n_exp = 4 * ones(25,1);