meansdevn

The meansdevn function returns the mean and standard deviation of a general lua table that may contain non-numeric values, named keys, and sub-tables. Only numeric values found in the table are used in the calculation. The meann function returns only the mean value. The related meansdev function calculates the mean and standard deviation of a 1-dimensional array, CImage, or list of numbers. Since an array is a specific type of table that contains only numbers or sub-tables, this function can also be used for arrays.

Syntax

nMean, nStdDev = meansdevn( tbl )

bullet.gif    tbl is a general lua table.

bullet.gif    nMean is the mean of the data.

bullet.gif    nStdDev is the standard deviation of the data.

Examples

The following script returns the mean and standard deviation of a 1-dimensional array containing 1 million random numbers.

t = random( 1000000 )

-- create an array of numbers

v, s = meansdevn( t )

-- find the mean & standard deviation

Printf("Mean=%lg, sdev=%lg\n", v, s )

-- list the result

  

The next example computes the mean and standard deviation of an ugly, complex table:

t = { 6, -2, 15, "a", {5,"b"}, c="5.4" }

 

v, s = meansdevn(t)

-- find the mean and standard deviation

Printf("M= %lg, S= %lg\n", v, s )

-- result: Mean = 6, based on only 4 numbers

Related Topics

Table and Array Functions, meann, mediann, sdevn, meansdev


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