unu jhisto: Create joint histogram of two or more nrrds. Each axis of the
output corresponds to one of the input nrrds, and each bin in the output
records the number of corresponding positions in the inputs with a combination
of values represented by the coordinates of the bin.
Usage: unu jhisto -i <nin0 nin1 ...> -b <bins0 bins1 ...> [-t <type>] \
[-o <nout>]
-i <nin0 nin1 ...> = All input nrrds (2 or more nrrds)
-b <bins0 bins1 ...> = bins<i> is the number of bins to use along axis i (of
joint histogram), which represents the values of nin<i>
(2 or more ints)
-t <type> = type to use for output (the type used to store hit
counts in the joint histogram). Clamping is done on hit
counts so that they never overflow a fixed-point type;
default: "uint"
-o <nout> = output nrrd (string); default: "-"
