Praat: Automatic Formant Extraction by time step

Question

I am performing some large-corpus analyses in Praat and have been extracting formant (F1, F2, F3) values at every 10% interval for my textgrids, but have decided that a much more even-handed measure would be to extract these parameters once every half-second or so in each of my intervals, but I can't seem to figure out how to automate this. I am trying to pull relatively randomized formant samples from my intervals as the corpus is far too large to reasonably annotate each vowel.

Does anyone know how to script this in Praat (specifically just the time-series)? Thanks.

For reference this is how I've been sampling:

    .time [1] = start + 0.1*(end-start)
    .time [2] = start + 0.2*(end-start)
    .time [3] = start + 0.3*(end-start)
    .time [4] = start + 0.4*(end-start)
    .time [5] = midpoint
    ....

Answer 1

The rest of the script is there: http://praatscriptingtutorial.com/filesExtendedExample

I haven't tested this script and my answer in Praat, so I cannot ensure that it will work.

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# We had made a variable intNum, now
# we'll use that as the counter variable
for intNum from 1 to numIntervals

    ###### Get F1 and F2 from midpoint

    selectObject: tg

    #Get its label
    label$ = Get label of interval: tierNum, intNum 

    # If not blank
    if label$ <> ""
        beg = Get starting point: tierNum, intNum
        end = Get end point: tierNum, intNum
                    length = end - beg
                    if length > 0.5
                    repeat
        midPoint = beg + 0.5

        selectObject: formantObj
        # First argument is formant number
        f1 = Get value at time: 1, midPoint, "Hertz", "Linear"
        f2 = Get value at time: 2, midPoint, "Hertz", "Linear"
                    f3 = Get value at time: 3, midPoint, "Hertz", "Linear"

        # Format the values and convert to string, 
        # to make it easier to write to the spreadsheet
        f1$ = fixed$: f1, 0
        f2$ = fixed$: f2, 0
                    f3$ = fixed$: f3, 0

                    beg = midpoint

                   until midpoint >= end

              endif

  endfor

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For further information about loops method in Praat: http://www.fon.hum.uva.nl/praat/manual/Scripting_5_4__Loops.html