length — length of object
n=length(M)
For usual or polynomial matrix n is the integer
equal to number of rows times number of columns of M.
(Also valid for M a boolean matrix)
For matrices made of character strings (and in particular for a
character string) length returns in
n the length of entries of the matrix of character
strings M.
The length of a list is the number of elements in the list (also
given by size).
length('123') is 3.
length([1,2;3,4]) is 4.
WARNING : length of a sparse matrix returns the max of dimensions and not the product of the dimensions. (example : length(sparse(eye(12,2))) returns max(12,2) and not 24)
please use size(...,'*') with sparse matrix.