SigmaXY Command
- SigmaXY( <List of Points> )
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Calculates the sum of the products of the x- and y-coordinates.
You can work out the covariance of a list of points using SigmaXY(list)/Length(list) - MeanX(list) * MeanY(list).
- SigmaXY( <List of x-coordinates>, <List of y-coordinates> )
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Calculates the sum of the products of the x- and y-coordinates.
Let A = (-3, 4), B = (-1, 4), C = (-2, 3) and D = (1, 3) be points.
{x(A), x(B), x(C), x(D)} yields the x-coordinates of the points in a list list1 = \{-3, -1, -2, 1} and
{y(A), y(B), y(C), y(D)} yields the y-coordinates of the points in a list list2 = \{4, 4, 3, 3}. Command
SigmaXY(list1, list2) yields a = -19.