Difference between revisions of "SigmaXY Command"

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; SigmaXY( <List of Points> )
 
; SigmaXY( <List of Points> )
 
:Calculates the sum of the products of the ''x''- and ''y''-coordinates.
 
: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>.}}
  
  
 
;SigmaXY( &lt;List of x-coordinates>, &lt;List of y-coordinates> )
 
;SigmaXY( &lt;List of x-coordinates>, &lt;List of y-coordinates> )
 
:Calculates the sum of the products of the ''x''- and ''y''-coordinates.
 
:Calculates the sum of the products of the ''x''- and ''y''-coordinates.
:{{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''.}}
+
:{{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''.}}

Latest revision as of 09:10, 12 October 2017


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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