meansdev

meansdev

The meansdev function returns the mean and standard deviation of a CImage, 1-dimensional array, or list of numbers. The mean function returns only the mean value. The array and list parameters must contain a mixture of explicit numbers and strings that can be converted to numbers. This function is similar to the CStat:Mean method but does not require calling new_stats() beforehand to create a CStats object. The mean function calculates only the mean of a 1-dimensional array, CImage, or list of numbers.

Whereas this function operates on a pure (indexed) array, the slightly slower meann and meansdevn functions calculate the mean and standard deviation for a general table that may be a multi-dimensional array or contain a mixture of numbers, strings, named keys, and sub-tables. Also see the mean function which returns only the mean value.

Syntax

nMean, nStdDev = meansdev( Data )

nMean, nStdDev = meansdev( n1, n2, n3, ... )

Data is a 1-dimensional array, list of numbers or a CImage object.

n1, n2, n3, ... are numbers or string values that can be converted to numbers.

nMean is the mean of the data.

nStdDev is the standard deviation of the data.

Remarks

The CImage class supports values ranging from byte to double plus other pixel types.

Examples

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

t = random( 1000000 )	-- create a table of numbers
v, s = meansdev( t )	-- find the mean & standard deviation
Printf("Mean=%lg, sdev=%lg\n", v, s )	-- list the result

The next script returns the mean and standard deviation for pixels inside a rectangle at the corner of a CImage.

V = AttachView( "CImageView" )	-- attach the topmost image window
Assert( V and V:Count() > 0 )	-- make sure an image window is on top
R = new_rect( 1, 20, 1, 40 )	-- rectangle for corner of image
v, s = meansdev( V:GetImage(), R )	-- use the current image in the CImageView
Printf("Mean=%lg, Sdev=%lg\n", v, s )	-- list the result

The next example computes the mean and standard deviation of a list of numbers:

v, s = meansdev( 5, 6, -2, 5.4 }	-- find the mean and standard deviation
Printf("M= %lg, S= %lg\n", v, s )	-- result: Mean = 3.6

Syntax

Remarks

Examples

Related Topics