Storing strings in waves

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Thu, 02/09/2012 - 01:30 pm

I am trying to recall strings from a wave. This seems to work OK, so long as the wave was created within the function itself, however, it gives unexpected results when I access the data from another function.

#pragma rtGlobals=1     // Use modern global access method.
Function test()
    make/T/O testTextWave={"text","goes","in","here"}
    print testTextWave
    print testTextWave[0]
End

Function testX()
    wave testTextWave
    print testTextWave
    print testTextWave[0]
End


If you run test(), you get the following output:
•test()
  testTextWave[0]= {"text","goes","in","here"}
  text
•testX()
  testTextWave[0]= {"text","goes","in","here"}
  3.37009e-275


can anyone tell me what I am doing wrong? The testX function can "see" the testTextWave just fine and print it in its entirety, but when asked to produce a single cell, it fails.
mtaylor wrote:


#pragma rtGlobals=1     // Use modern global access method.
Function test()
    make/T/O testTextWave={"text","goes","in","here"}
    print testTextWave
    print testTextWave[0]
End

Function testX()
    wave testTextWave
    print testTextWave
    print testTextWave[0]
End



In your function TestX() you have to declare testtextwave was a text wave using the /T flag, otherwise, Igor will assume that it is numerical.

Function testX()
    wave/T testTextWave
    print testTextWave
    print testTextWave[0]
End

February 9, 2012 at 01:46 pm - Permalink

It should be:
Function testX()
    wave/t testTextWave
    print testTextWave
    print testTextWave[0]
End


I don't know why the print testTextWave in the testX version in the original version worked though.

February 9, 2012 at 01:47 pm - Permalink

AH, ok! I had a similar issue earlier when dealing with complex variables. Thanks!
variable/c varname


Was required to hold temporary values. This may seem obvious to everyone out there, but it took me hours of reading to figure it out.

February 9, 2012 at 01:52 pm - Permalink

here's a followup:

The following function makes a string that I want to feed into another function. I can make the string just fine...
Function/s makeparslist() // makes a string to feed the display command
    wave/t coeffnames
    variable ii,cnum=numpnts(coeffnames)
    string parslist = "pars[0][*]"
    for(ii = 1 ; ii < cnum ; ii += 1)
        parslist += ",pars["+num2istr(ii)+"][*]"
    endfor
    return parslist
End

but I'm not sure how to feed it into the display command
Display makeparslist()


tells me that I am using the wrong datatype, which makes sense... display is expecting a wave, and i've fed it a string... the string contains a list of wavenames in what should be the proper syntax, but I can't seem to bridge the gap here. Is this even possible to do, or do I need to do this a different way? (I have worked out a loop to append traces to the graph one at a time, but thought this would be more elegant.

February 9, 2012 at 04:21 pm - Permalink

I ended up solving it in a different way. Shame, I was excited about my concatenated strings.

February 9, 2012 at 04:45 pm - Permalink

Don't give up just yet. There is a way to use display + string function, albeit a bit clumsy one:

Execute "Display " + makeparslist()


Execute is for executing strings as commands, but there are often better ways to do things.

February 10, 2012 at 06:08 am - Permalink

mtaylor wrote:
here's a followup: ... I can make the string just fine...
....but I'm not sure how to feed it into the display command
Display makeparslist()



When your string of wavenames is in a semi-colon separated list called ywavelist, where every wave is in the currrent data folder or has explicit path designations, and each wave is a scaled wave, you could also do ...

Display
LinkDisplay#LAppendtoGraph(ywavelist)


In case each y-wave needs to be plotted versus a specific x-wave, you can also use "linking" functions first, and then repeat the above for the proper outcome.

The Execute command is encapsulated in the LinkDisplay functions.

http://www.igorexchange.com/project/LinkDisplay

--
J. J. Weimer
Chemistry / Chemical & Materials Engineering, UAHuntsville

February 10, 2012 at 10:43 am - Permalink

Thanks for the advice! I am using the "execute" command to solve another part of the code at your suggestion and it's working great! As for the string lists, I saw that earlier while reading the manual but I'm not sure how if will help me in this case. It certainly could come in handy later though.

February 11, 2012 at 11:39 pm - Permalink