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FFTSmooth v1

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Warning

FFTSmooth is deprecated. Use FFTSmooth version 2 instead.

Summary

Performs smoothing of a spectrum using various filters.

Properties

Name	Direction	Type	Default	Description
InputWorkspace	Input	MatrixWorkspace	Mandatory	The name of the input workspace.
OutputWorkspace	Output	MatrixWorkspace	Mandatory	The name of the output workspace.
WorkspaceIndex	Input	number	0	Workspace index for smoothing
Filter	Input	string	Zeroing	The type of the applied filter. Allowed values: [‘Zeroing’]
Params	Input	string		The filter parameters

Description

FFTSmooth uses the FFT algorithm to create a Fourier transform of a spectrum, applies a filter to it and transforms it back. The filters remove higher frequencies from the spectrum which reduces the noise.

This version of the FFTSmooth algorithm has one filter:

Zeroing

• Filter: “Zeroing”

• Params: “n” - an integer greater than 1 meaning that the Fourier coefficients with frequencies outside the 1/n of the original range will be set to zero.

Usage

Example: Zeroing with Params=2

ws = CreateSampleWorkspace(function="Multiple Peaks",XMax=20,BinWidth=0.2,BankPixelWidth=1,NumBanks=1)

#add a bit of predictable noise
noiseAmp=0.1
noiseArray= []
for i in range(ws.blocksize()):
    noiseAmp = -noiseAmp
    noiseArray.append(noiseAmp)

for j in range(ws.getNumberHistograms()):
    ws.setY(j,ws.readY(j)+noiseArray)


wsSmooth = FFTSmooth(ws, Params='2', Version=1)

print("bin Orig  Smoothed")
for i in range (0,100,10):
    print("{}  {:.2f}  {:.2f}".format(i, ws.readY(0)[i], wsSmooth.readY(0)[i]))

Output:

bin Orig  Smoothed
0  0.20  0.30
10  0.20  0.30
20  0.37  0.47
30  10.20  10.30
40  0.37  0.47
50  0.20  0.30
60  8.20  8.30
70  0.20  0.30
80  0.20  0.30
90  0.20  0.30

Categories: AlgorithmIndex | Arithmetic\FFT | Transforms\Smoothing | Deprecated

Source

C++ header: FFTSmooth.h

C++ source: FFTSmooth.cpp