# Difference between revisions of "SigmaXX Command"

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## Revision as of 11:10, 29 July 2015

- SigmaXX[ <List of Points> ]
- Calculates the sum of squares of the
*x*-coordinates of the given points. **Example:**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.
**Example:**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.
**Example:**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*.