Copying selected data from one wave into a new wave

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Wed, 02/19/2014 - 01:36 am

Hi, new user here.

I have a wave with one column of numbers. I want to select all of the numbers in the wave greater than say, x, and copy them in to a new wave.

I'm basically completely lost. Thanks for your help!
Here is one way of doing it.
Hope this helps.
Function Test()
    // make some test data
    Make/O/N=10 wData={5,3,4,5,6,2,1,7,0,9}
    // copy to a 'result' wave
    Duplicate/O wData,wFilteredData
    // use conditional to set certain values to NaN
    wFilteredData[] = wFilteredData[p]>5 ? wFilteredData[p] : NaN
    // remove the NaNs
    WaveTransform zapNaNs wFilteredData
    // display the data in a table
    Edit wData,wFilteredData
End

February 19, 2014 at 01:48 am - Permalink

Thanks for replying. I tried your suggestion and got this message:
An attempt was made to treat a text wave as if it were a numeric wave.

I didn't think I had a text wave... The example with your wData wave works though.

February 19, 2014 at 02:03 am - Permalink

you can convert your data:

Make/N = (numpnts(tWave)) nWave
nWave = str2num(tWave[p])


where tWave is your text wave.

February 19, 2014 at 02:12 am - Permalink

Sorry for all the questions but when I try to compile I get an error saying:

"got 'tWave' instead of a string variable or string function name"
nWave = str2num(tWave[p])

February 19, 2014 at 02:30 am - Permalink

In a function you need to tell Igor that the text wave is a text wave. Try this:

function convert(tWave, threshold)
    wave/T twave
    variable threshold
   
    Make/O/N=(numPnts(twave)) nwave
    nwave = str2num(twave[p])
   
    nwave = nwave>threshold ? nwave : NaN
    WaveTransform zapNaNs nwave
end

February 19, 2014 at 02:51 am - Permalink

Guys, guys!

Function Test()
    // make some test data
    Make/O/N=10 wData={5,3,4,5,6,2,1,7,0,9}
    // extract values > 5
    Extract wData, wFilteredData, wData > 5
    // display the data in a table
    Edit wData,wFilteredData
End


--Jim Prouty
Software Engineer, WaveMetrics, Inc.

February 19, 2014 at 11:24 am - Permalink

JimProuty wrote:
Guys, guys!

Function Test()
    // make some test data
    Make/O/N=10 wData={5,3,4,5,6,2,1,7,0,9}
    // extract values > 5
    Extract wData, wFilteredData, wData > 5
    // display the data in a table
    Edit wData,wFilteredData
End



hm, yes, shorter but not necessarily faster…well, at least not on large data sets ;-)

function speed1(w)
    wave w
    variable num = StartmsTimer
   
    Duplicate/O w nw
    Multithread nw = w > 3 ? w : NaN
    Wavetransform zapNaNs nw
    print Stopmstimer(num)/1e6
end

function speed2(w)
    wave w
    variable num = StartmsTimer
   
    Extract/O w, nw, w > 3
    print Stopmstimer(num)/1e6
end


•make/N=1e7 test = enoise(5)
•speed1(test)
  0.509921
•speed2(test)
  1.08944

February 19, 2014 at 11:17 pm - Permalink