Perhaps this example due to Winston Chang is helpful:
Shiny example app with dynamic number of plots
Here is the full example just in case of linkrot:
server.R
max_plots <- 5
shinyServer(function(input, output) {
# Insert the right number of plot output objects into the web page
output$plots <- renderUI({
plot_output_list <- lapply(1:input$n, function(i) {
plotname <- paste("plot", i, sep="")
plotOutput(plotname, height = 280, width = 250)
})
# Convert the list to a tagList - this is necessary for the list of items
# to display properly.
do.call(tagList, plot_output_list)
})
# Call renderPlot for each one. Plots are only actually generated when they
# are visible on the web page.
for (i in 1:max_plots) {
# Need local so that each item gets its own number. Without it, the value
# of i in the renderPlot() will be the same across all instances, because
# of when the expression is evaluated.
local({
my_i <- i
plotname <- paste("plot", my_i, sep="")
output[[plotname]] <- renderPlot({
plot(1:my_i, 1:my_i, xlim = c(1, max_plots), ylim = c(1, max_plots), main = paste("1:", my_i, ". n is ", input$n, sep = ""))
})
})
}
})
ui.R
shinyUI(pageWithSidebar(
headerPanel("Dynamic number of plots"),
sidebarPanel(
sliderInput("n", "Number of plots", value=1, min=1, max=5)
),
mainPanel(
uiOutput("plots") # This is the dynamic UI for the plots
)
))