\(\renewcommand\AA{\unicode{x212B}}\)

ReplaceSpecialValues v1

Enable screenshots using DOCS_SCREENSHOTS in CMake

Summary

Replaces instances of NaN and infinity in the workspace with user defined numbers. If a replacement value is not provided the check will not occur. This algorithm can also be used to replace numbers whose value is larger than a user-defined threshold.

Properties

Name	Direction	Type	Default	Description
InputWorkspace	Input	MatrixWorkspace	Mandatory	The name of the input workspace
OutputWorkspace	Output	MatrixWorkspace	Mandatory	The name to use for the output workspace (can be the same as the input one).
NaNValue	Input	number	Optional	The value used to replace occurrences of NaN (default: do not check).
NaNError	Input	number	0	The error value used when replacing a value of NaN
InfinityValue	Input	number	Optional	The value used to replace occurrences of positive or negative infinity (default: do not check).
InfinityError	Input	number	0	The error value used when replacing a value of infinity
BigNumberThreshold	Input	number	Optional	The threshold above which a number (positive or negative) should be replaced. (default: do not check)
BigNumberValue	Input	number	0	The value with which to replace occurrences of ‘big’ numbers.
BigNumberError	Input	number	0	The error value used when replacing a ‘big’ number
SmallNumberThreshold	Input	number	Optional	The threshold below which a number (positive or negative) should be replaced. (default: do not check)
SmallNumberValue	Input	number	0	The value with which to replace occurrences of ‘small’ numbers.
SmallNumberError	Input	number	0	The error value used when replacing a ‘small’ number
CheckErrorAxis	Input	boolean	False	Whether or not to also check the error axis values.
UseAbsolute	Input	boolean	True	Whether large and small comparisons should be done on absolute values.

Description

The algorithm searches over all of the values, in Y and Error (provided the checkbox ‘CheckErrorAxis’ is ticked) axes, in a workspace and if it finds a value set to NaN (not a number), infinity, larger or smaller than the ‘big’/’small’ threshold given then that value and the associated error is replaced by the user provided values.

If no value is provided for either NaNValue, InfinityValue, BigValueThreshold or SmallValueThreshold then the algorithm will exit with an error, as in this case it would not be checking anything.

The algorithm can also handle event workspaces.

Usage

Example

import numpy as np
ws = CreateSampleWorkspace(BankPixelWidth=1)

yArray = np.array(ws.readY(0))
yArray[0] = 8e80
yArray[1] = float("inf")
yArray[2] = float("-inf")
yArray[3] = float("NaN")
yArray[4] = 8e-7
ws.setY(0,yArray)

ws = ReplaceSpecialValues(ws,NaNValue=0,InfinityValue=1000,
 BigNumberThreshold=1000, BigNumberValue=1000,
 SmallNumberThreshold=1e-6, SmallNumberValue=200)

print("i\tBefore\tAfter")
print("-\t------\t-----")
for i in range(5):
    print("{}\t{}\t{}".format(i, yArray[i],ws.readY(0)[i]))

Output:

i       Before  After
-       ------  -----
0       8e+80   1000.0
1       inf     1000.0
2       -inf    1000.0
3       nan     0.0
4       8e-07   200.0

import numpy as np
ws = CreateSampleWorkspace(BankPixelWidth=1)

value1 = 1.00000004
value2 = 1.00000003
valueDiff = value1 - value2

wsYArray = np.array(ws.readY(0))
wsYArray[0] = valueDiff
ws.setY(0, wsYArray)
ws = ReplaceSpecialValues(ws, SmallNumberThreshold=1e-6)

print("Before\t\t After")
print("{0:.11e}\t{1:.1f}".format(wsYArray[0], ws.readY(0)[0]))

Output:

Before                After
9.99999993923e-09   0.0

Categories: AlgorithmIndex | CorrectionFunctions\SpecialCorrections

Source

C++ header: ReplaceSpecialValues.h

C++ source: ReplaceSpecialValues.cpp