sdev

sdev (replaces TSdev)

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

Whereas this function operates on a pure (indexed) array, the slightly slower sdevn function operates on a general table that may be a multi-dimensional array or contain a mixture of numbers, strings, named keys, and sub-tables.

The related sdevxn function computes the standard deviation about a specified value for a general table.

Syntax

nStdDev = sdev( Data )

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.

nStdDev is the standard deviation of the values.

Remarks

Except for the CImage class, the members of Data are interpreted as numbers with pixel type "double". The CImage class supports values ranging from byte to double plus other pixel types.

Examples

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

t = random( 1000000 )	-- create a table of numbers
sd = sdev( t )	-- find the standard deviation
Printf("Sdev= %lg\n", sd )	-- list the result

The next script returns the 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
sd = sdev( V:GetImage(), R )	-- use the current image in the CImageView
Printf("Sdev= %lg\n", sd )	-- list the result

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

s = sdev( 5, 6, -2, 5.4 }	-- find the standard deviation
Printf("SDev = %lg\n", m )	-- result: SDev = 3.12

Syntax

Remarks

Examples

Related Topics