Difference between revisions of "SigmaXY Command"

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

Revision as of 12:32, 16 July 2013




SigmaXY[ <List of Points> ]
Calculates the sum of the products of the x- and y-coordinates.
Example: 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> ]
Calculates the sum of the products of the x- and y-coordinates.
Example: 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.
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