AddLogDerivative v1

../_images/AddLogDerivative-v1_dlg.png

AddLogDerivative dialog.

Summary

Add a sample log that is the first or second derivative of an existing sample log.

Properties

Name Direction Type Default Description
InputWorkspace InOut MatrixWorkspace Mandatory An input/output workspace. The new log will be added to it.
LogName Input string Mandatory The name that will identify the log entry to perform a derivative. This log must be a numerical series (double).
Derivative Input number 1 How many derivatives to perform. Default 1.
NewLogName Input string   Name of the newly created log. If not specified, the string ‘_derivativeN’ will be appended to the original name

Description

This algorithm performs a simple numerical derivative of the values in a sample log.

The 1st order derivative is simply: dy = (y1-y0) / (t1-t0), which is placed in the log at t=(t0+t1)/2

Higher order derivatives are obtained by performing the equation above N times. Since this is a simple numerical derivative, you can expect the result to quickly get noisy at higher derivatives.

If any of the times in the logs are repeated, then those repeated time values will be skipped, and the output derivative log will have fewer points than the input.

Usage

Example: Taking the derivative of logs

ws = CreateSampleWorkspace()
AddTimeSeriesLog(ws,"MyLog","2010-01-01T00:00:00",1.0,DeleteExisting=False)
AddTimeSeriesLog(ws,"MyLog","2010-01-01T00:00:10",2.0,DeleteExisting=False)
AddTimeSeriesLog(ws,"MyLog","2010-01-01T00:00:20",0.0,DeleteExisting=False)
AddTimeSeriesLog(ws,"MyLog","2010-01-01T00:00:30",5.0,DeleteExisting=False)

AddLogDerivative(ws,"MyLog",derivative=1,NewLogName="Derivative1")
AddLogDerivative(ws,"MyLog",derivative=2,NewLogName="Derivative2")
AddLogDerivative(ws,"MyLog",derivative=3,NewLogName="Derivative3")

for logName in ["MyLog","Derivative1","Derivative2","Derivative3"]:
    print "Log: " + logName
    print ws.getRun().getProperty(logName).valueAsString()

Output:

Log: MyLog
2010-Jan-01 00:00:00  1
2010-Jan-01 00:00:10  2
2010-Jan-01 00:00:20  0
2010-Jan-01 00:00:30  5

Log: Derivative1
2010-Jan-01 00:00:05  0.1
2010-Jan-01 00:00:15  -0.2
2010-Jan-01 00:00:25  0.5

Log: Derivative2
2010-Jan-01 00:00:10  -0.03
2010-Jan-01 00:00:20  0.07

Log: Derivative3
2010-Jan-01 00:00:15  0.01

Categories: Algorithms | DataHandling\Logs