covar
=====

covariance of two variables



Calling Sequence
~~~~~~~~~~~~~~~~


::

    s=covar(x,y,fre)




Arguments
~~~~~~~~~

:x real or complex vector
: :y real or complex vector
: :fre matrix of type length(x) x length(y)
:



Description
~~~~~~~~~~~

`covar(x,y,fre)` computes the covariance of two variables x and y. fre
is a matrix of dimensions length(x) x length(y). In fre the element of
indices (i,j) corresponds to the value or number or frequences of
x_i&y_j.



References
~~~~~~~~~~

Wonacott, T.H. & Wonacott, R.J.; Introductory Statistics, J.Wiley &
Sons, 1990.



Examples
~~~~~~~~


::

    x=[10 20 30 40]
    y=[10 20 30 40]
    fre=[.20 .04 .01  0;
         .10 .36 .09  0;
           0 .05 .10  0;
           0   0   0 .05]
    s=covar(x,y,fre)