Shimmer functions won't run on textgrid intervals but jitter functions work fine?

Question

I am trying to make a praatscript that extracts jitter and shimmer values from each interval of a textgrid (phoneme).

I define all necessary objects before looping through the intervals, and then call jitter or shimmer at each interval. All jitter functions work fine, but shimmer functions produce an error:

"Command "Get shimmer (local)..." not available for current selection."

I can't figure out the cause of this. I don't see a reason why jitter works for the selection but not shimmer. The praatscript is as follows.

select Sound 'thisSound$'
To Pitch (ac): 0, 100, 15, "yes", 0.03, 0.45, 0.01, 0.35, 0.14, 500
select Sound 'thisSound$'
To PointProcess (periodic, cc)... 100 500
select Sound 'thisSound$'
To Harmonicity (cc)... 0.01 100 0.1 1

# Loop through each interval on the phoneme tier.
for thisInterval from 1 to numberOfPhonemes
    # Get the label of the interval
    select TextGrid 'thisTextGrid$'
    thisPhoneme$ = Get label of interval: 1, thisInterval
    
    # Jitter measurements
    select PointProcess 'thisSound$'
    meanlocaljitter = Get jitter (local)... thisPhonemeStartTime  thisPhonemeEndTime  0.0001 0.02 1.3

    select PointProcess 'thisSound$'
    meanlocalshimmer =  Get shimmer (local)... thisPhonemeStartTime thisPhonemeEndTime 0.0001 0.02 1.3 1.6

I have tried not reselecting the PointProcess. I have also tried other variations of shimmer functions with no success.. I dont understand why the shimmer command can't run on the selection if the jitter command can?

Thanks for your help!

Answer 1

For the shimmer command, you need to have a sound object and a point process object selected.

So add something like the following before the line where you run the shimmer command:

selectObject: "Sound 'thisSound$'", "PointProcess 'thisSound$'"