CStats:RankClipMean

The RankClipMean method computes the mean and standard deviation for a data sample, excluding thenHigh highest and nLow lowest values from the sample. The sample may be a Lua table or a class object of type CImage, CArray, or CMatrix. For CImage and CMatrix objects, an optional CRect object can be used to define the points used in the calculation.

Syntax

nMean, nStdDev = CStats:RankClipMean( table, nHigh, nLow )

nMean, nStdDev = CStats:RankClipMean( CImage, nHigh, nLow )

nMean, nStdDev = CStats:RankClipMean( CImage, nHigh, nLow, CRect )

nMean, nStdDev = CStats:RankClipMean( CArray, nHigh, nLow )

nMean, nStdDev = CStats:RankClipMean( CArray, nHigh, nLow, CRect )

nMean, nStdDev = CStats:RankClipMean( CMatrix, nHigh, nLow )

where

table is a lua table containing the data.

CImage, CArray, and CMatrix are class objects containing the data to measure,

CRect is a CRect rectangle object that defines the region to measure.

nHigh and nLow specify the high and low percentiles in the range 0 through 100.

nMean and nStdDev are the rank-clipped mean and standard deviation of the data. On failure, 0,0 is returned.

The calculated statistic computes the mean value using data above a low percentile and below a high percentile rank. These rank percentiles are absolute on the scale 0 to 100 percent. For example, passing the argumentsnHigh=95 and nLow=5 calculates the region mean value after excluding values in both the upper 5 percentile and the lower 5 percentile of the sample.

This method uses the same algorithm as the RankClip method of the CImCombine class.

Examples

Suppose a CImage I and a CRect R exist. The following script returns the rank clipped mean value inside a rectangle on the image. Clipping is done at the 95th percentile and 3rd percentile:

S = CStats:new()	-- create a CStats object
nMean = S:RankClipMean( I, 95, 3, R )	-- mean value between 5th and 95th percentile
Printf("mean=%lg\n", nMean )	-- list the results

The following script returns the rank-clipped mean value for a table of data. Clipping is done at the 95th percentile and 3rd percentile:

S = CStats:new()	-- create a CStats object
t = { 4,1,4,2,2.1,5,6.4,2,-1.4,-.5,3,4 }	-- create some data in a table
Printf("mean=%lg\n", S:RankClipMean(t,95,3) )	-- list the result