In
mathematics, an
incidence matrix is a
matrix that shows the relationship between two classes of objects. If the first class is
X and the second is
Y, the matrix has one row for each element of
X and one column for each element of
Y. The entry in row
x and column
y is 1 if
x and
y are related (called
incident in this context) and 0 if they are not. There are variations; see below.