Creating JSON files for jsPSych experiments with R #1526

JAQuent · 2021-02-17T18:45:31Z

JAQuent
Feb 17, 2021

Hey,
I thought some might like this pipeline. What I like do for my jsPsych experiments, is to code all the trial information in R and hardcode that information into a .js file that I than load before the experiment.

For instance, I can take a data.frame in R like this one:

# My data.frame with all experimental variables
df <- data.frame(a = 1:2, b = 3:4)

# Creating a .js file from this
json_strings_from_df(df, 'example.js')

This particular function can be found here. This example .js file looks like this:

var a = "[1,2]";

a = JSON.parse(a);

var b = "[3,4]";

b = JSON.parse(b);

When I now run this
<script src="scene_repetition2_studyTask_trials.js"></script>
in the <head></head> part, then I can use variables a and b in my experiment. If I want I can use them as timeline variables. For that, I just create an array and use a simple for loop to assign the values to that array.

var trials = new Array();
var nTrial = a.length();
for (i = 0; i < nTrial; i++){
trials[i] = {a[i],
	         data: {b: b[i]};

};

then this arrary can be used like this

  var blank = {
    type: 'html-keyboard-response',
    stimulus: '',
    choices: jsPsych.NO_KEYS,
    data: jsPsych.timelineVariable('data'),
    trial_duration: jsPsych.timelineVariable('a'),
  };

and then it has to be added to the timeline like this

  var experiment = {
    timeline: [blank],
    timeline_variables: trials,
  };
  timeline.push(experiment);

If I have multiple counter balancing conditions, I use lists like this:

a1 <- c(1, 2)
a2 <- c(4, 5)
a  <- list(a1, a2)

create_json_variable_str('a', a)

This creates a string like this

"var a = \"[[1,2],[4,5]]\";" and I just have to write this one to .js file and add a = JSON.parse(a); and I can access the correct a for my particular condition by choosing a[0] vs. a[1].

The function can be found here.

Note sure if that's the most elegant way to handle this kind of stuff but since I am more proficient in R prefer this and maybe it's helpful for someone else.

becky-gilbert · 2021-02-18T18:51:19Z

becky-gilbert
Feb 18, 2021
Maintainer

This is very cool. Thanks for sharing!

0 replies

cvanheer · 2023-05-07T03:38:56Z

cvanheer
May 7, 2023

Just wanted to say thanks cos I simulate my trials in R as well and was tossing up between doing csv -> json -> js but I realise I can just do the json bit in R as well so thank you :) @JAQuent!

0 replies

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Creating JSON files for jsPSych experiments with R #1526

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Creating JSON files for jsPSych experiments with R #1526

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JAQuent Feb 17, 2021

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becky-gilbert Feb 18, 2021 Maintainer

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cvanheer May 7, 2023

JAQuent
Feb 17, 2021

becky-gilbert
Feb 18, 2021
Maintainer

cvanheer
May 7, 2023