SigmaXX Command

SigmaXX( <List of Points> ): Calculates the sum of squares of the x-coordinates of the given points.

Let list1 = {(-3, 4), (-1, 4), (-2, 3), (1, 3), (2, 2), (1, 5)} be a list of points. SigmaXX(list1) yields the value 20.

SigmaXX( <List of Raw Data> ): Calculates the sum of squares of the given numbers.

In order to work out the variance of a list you may use SigmaXX(list) / Length(list) - Mean(list)^2.

SigmaXX( <List of Numbers>, <List of Frequencies> ): Calculates the weighted sum of squares of the given numbers.

Let list1 = {3, 2, 4, 3, 3, 2, 1, 1, 2, 3, 3, 4, 5, 3, 2, 1, 1, 2, 3} be a list of numbers. Unique(list1) yields list2 = {1, 2, 3, 4, 5} and Frequency(list1) yields list3 = {4, 5, 7, 2, 1}. Command SigmaXX(list2, list3) yields the value 144.