Returning a wave from function

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Tue, 01/05/2021 - 02:51 am

Hi,

I have edited the following code:

 

Function PP()
Make /O /N=100 toto
toto=X*2

duplicate /O  toto tata
tata= gen_w(toto)
edit tata

End


Function gen_w(name)
wave name

duplicate /O name H
H=name/100
return H

End

 

When I execute PP(), tata is filled with expected values. It works well.

From the Command Window, if I execute:

print gen_w(toto)

only the first value of the wave (0) is printed. I was expecting an editing of the full wave.

Why am I wrong?

 

Thanks for your help.

Erik

In modern Igor environments your example does not even compile. The reason is that the return statement of a normal function is giving back a single (scalar double-precision) number. If you want to return a wave (reference) you need the /WAVE flag. Try this:

Function PP()
    Make /O /N=100 toto=X*2
    duplicate /O  toto tata
    Wave workwave = gen_w(toto)
    tata=workwave
    edit tata
End

Function/WAVE gen_w(name)
    wave name
    duplicate /O name H
    H=name/100
    return H
End

Print will still give you just a single point, though (which you can choose now however). For example, to print the 10th point of the returned wave use:

print gen_w(toto)[10]

 

January 5, 2021 at 03:06 am - Permalink

And another mysterious thing:

executing:

 

Function PP()
Make /O /N=100 toto
toto=X*2

duplicate /O  toto tata, titi
tata= gen_w(toto)
//titi=gen_w(toto)*2


End


Function gen_w(name)
wave name

duplicate /O name H
H=name/100
return H

End

modifies as well the existing titi file, but the command line in the code is now a comment, and this file should not change.

I guess there is an issue in my understanding of wave manipulation.

 

Erik

January 5, 2021 at 03:13 am - Permalink

Thank you. It works. There is however still the strange issue if the function is called twice. I mean, if the following code is executed:

 

Function PP_corr()
    Make /O /N=100 toto=X*2
    duplicate /O  toto tata,titi
    Wave workwave = gen_w(toto)
    tata=workwave
//    Wave workwave1=gen_w(toto)
//   titi=workwave1*2

End

Function/WAVE gen_w(name)
    wave name
    duplicate /O name H
    H=name/100
    return H
End

 

The titi file is modified by the program, but the corresponding lines that should update tit have been cancelled.

What is wrong?

 

Thanks.

 

January 5, 2021 at 03:21 am - Permalink

Wave references (and other types of references) can be confusing when you first encounter them. I might suggest some reading:

DisplayHelpTopic "Accessing Global Variables And Waves"

DisplayHelpTopic "Wave References"

DisplayHelpTopic "Accessing Waves In Functions"

January 5, 2021 at 11:26 am - Permalink