CODEWITHSUNDEEP
rshiny
Justace Clutter
Justace Clutter

Reputation: 2186

Method to Loop Through a List in a Shiny Reactive Render Function

I have generated a series of plots that I would like to loop through when generating a dynamic number of plots in a Shiny application. In the server function I have an observe function with the following structure:

server = function(input, output, session) {

    <Lots of other code>

    plotlist = generate_list_of_plots()
    for(i in seq_len(length(plot list))) {
        plotname = sprintf('ui_plot_%i', i)
        output[[plotname]] = renderPlot(plotlist[[i]])
    }

    <Lots of other code>

}

Unfortunately, this does not function as I would like as the last plot in the list is repeated for each of the correlated plotOutput objects which were generated in a separate block of code. I believe this behavior is related to the fact that the renderPlot expressions are not called until the plots are made visible when the user clicks on a tab and the i indexing variable has been advanced to its final position and is static each time the renderPlot function is executed, and therefore I get the same plot.

1: Is this the true cause of the issue? 2: If it is, what is the correct way to handle this type of situation?

Upvotes: 0

Views: 1061

Answers (1)

Justace Clutter
Justace Clutter

Reputation: 2186

It seems as though I was able to locate a solution to the problem. I was correct in my assumption and the answer is the local function. The solution was found in this post.

The corrected code would be the following:

server = function(input, output, session) {

    <Lots of other code>

    plotlist = generate_list_of_plots()
    for(i in seq_len(length(plot list))) {
        local({
            my_i = i
            plotname = sprintf('ui_plot_%i', my_i)
            output[[plotname]] = renderPlot(plotlist[[my_i]])
        })
    }

    <Lots of other code>

}

Upvotes: 1

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