Handling wave data point as $wave in a function

If the wave doesn't already exist, then you're making it correctly.

Just in case you are unaware, ww[1] is the second value in the wave; ww[0] is the first.

Also, ww(val) is different than ww[val]. The first uses X scaling to locate a value, the second uses the point number (row number in a 1D wave).

Thank you very much. And also thanks for [ vs ().

I do not understand why one need to copy the wave. In a macro, it is not necessary. Would you know why it changed?

Execute this:

DisplayHelpTopic "Wave References"

I recommend that you, and anyone else doing Igor programming, read the Programming help file. It will take a few cycles of reading/programming before everything sinks in.

I do not understand why one need to copy the wave. In a macro, it is not necessary. Would you know why it changed?

 

You don't need to copy the wave in a function if the wave already exists, you only need to create a wave reference (a pointer to the wave):

Function SSA(name)
    String name // name of existing wave
 
    Wave ww=$name
 
    Variable i, n= numpnts(ww)
    for(i=0; i<n; i+=1 )
        ww[i]= i
    endfor
End

 If it were me, I would rewrite SSA to take wave parameter. the function can be called from a Macro or the command line by using the name of an existing wave:

Macro moo()
    SSAW(ww)
End
 
 
Function SSAW(w)
    Wave w // reference to existing wave
 
    Variable i, n= numpnts(w)
    for(i=0; i<n; i+=1 )
        w[i]= i
    endfor
 
End