Problem with JavaScript conversion - Pavlovia stuck on "intializing experiment" screen

Online experiments
1

URL of experiment: https://run.pavlovia.org/t_s/24drb_erw/html

Description of the problem: Pavlovia is stuck on the “intializing experiment” screen.
I have read on other forum posts that one reason could be the python to js conversion, and I think this might be my problem.

I have built the experiment with the PsychoPy Builder, and have a few custom code elements in it.
The code element that I think might be causing the problem is one I used to set the interval between the fixation cross and the first stimulus (the other code elements have been used before). I tried this out in the offline version of the experiment, and it works as I want it to. Basically, it uses numpy’s random.exponential function to set the interval between two stimuli. If the interval that is drawn is too long then it is rejected with a if statement.

Below is the python code I am using in the Begin Routine tab:

from numpy import random
sc = 0.2
maxi = sc * 12.5

#generate number
isi = random.exponential(scale = 0.2, size = None)
#if isi is larger than maxi, keep drawing until it is smaller
while isi > maxi:
    #print("larger")
    isi = random.exponential(scale = 0.2, size = None)

thisExp.addData("isi", isi)

In the Begin Experiment tab I have:
isi = 0

In the Duration field of the respective Routine, I use “$isi” to set the duration.

Since this works offline but not online, I guess this has something to do with the conversion to javascript? Or can I not import python libraries online? I don’t really know javascript, so I am not sure where the problem lies.

Any help would be appreciated.

Cheers,
tasi

2

Please look at my crib sheet for how to define random variables.

Would this work for randexp if defined in code_JS or am I misreading the function?

randexp = function(scale) {
  return Math.exp(-Math.random()/scale)/scale;
}
3

Hello,

You can’t import Python libraries online. PsychoPy imports a set of libraries and their equivalent JavaScript-counterparts.

Best wishes Jens

4

thanks so much for the function in js code and for pointing me towards the crib sheet.

However after taking a look at the implementation of numpys random.exponential function (python - How to view the source code of numpy.random.exponential? - Stack Overflow) and translating it to js, it looks like this might be a closer approximation of the function

randexp = function(scale) {
  return -scale*Math.log(1.0-Math.random());
}

I would be very happy for any feedback on this.

thanks again for your help :slight_smile:

5

Hey,

thanks for the reply. I just found it in the crib sheet mentioned in @wakecarter 's comment (which I should have read before starting!)

cheers,
tasi