Shiny session random sampling

[StefanMunnes]

Description

I am currently conducting my self-made wiki survey and have stumbled across a strange behavior:

In the app.R file, I load an Excel file with items from which I randomly select 10 pairs for respondents to choose their most popular one.

I was expecting the sample to be redrawn each time the shiny survey page was opened. After looking at the first few responses, I have seen that this is not the case, and multiple responses get the same sample pairs in the same order. It seems like the item pairs are only randomly selected every few hours and not every time the page is reopened.

Is this a property of the Shiny server? Can this be changed via a setting? Does it change if I write the load and randomize in the server() function?

[StefanMunnes]

Okay, I found the solution. Putting the sampling of the pairs in the server() function does the job.
https://stackoverflow.com/questions/70225150/do-random-functions-such-as-sample-work-when-i-deploy-a-shiny-app

If you think this could be helpful to others, I can keep this post, otherwise we can delete it.

[jhelvy]

This is in the docs already on setting up randomization: https://surveydown.org/manuals/reactivity#pre-defined-randomization

It's a bit buried, maybe we should move this to a separate manual on "randomization"? Randomizing things across respondents is a common thing people might want to do.

[StefanMunnes]

I'm sorry, my bad! But yes, I would agree, it would be better if there is also a more general section in the manual about randomization and highlight the part with the server function.

Thanks and all the best!

[jhelvy]

Okay, I just broke out this section and moved it into it's own page: https://surveydown.org/manuals/randomization

We can update that manual further if we have other specific examples that are helpful.