Dynamically change plots based on user input in Shiny - r

Question

I'm trying to create a shiny app that generates plots based on the user selection of a subset of a loaded dataframe. For example, I have the following dataset:
library(shiny)
library(data.table)
df <- rbind(
data.table( cat = rep('X', 40), grp = rep(LETTERS[1:4], each=10), x = rep(1:10, times=4), y = rnorm(40) ),
data.table( cat = rep('Y', 30), grp = rep(LETTERS[1:3], each=10), x = rep(1:10, times=3), y = rnorm(30) ),
data.table( cat = rep('Z', 20), grp = rep(LETTERS[4:6], each=10), x = rep(1:10, times=2), y = rnorm(20) )
)
Based on the value for cat that the user selects in the UI, I want shiny to produce charts for each value of grp. So, if the user selects 'X', then there will be 4 plots produced; if they select 'Y' there will be three, and if they select 'Z' there will be 3.
I also want to specify how each chart is generated based on the value of grp. So if grp is A,D or E I want it produce a line plot, otherwise it should produce a scatterplot (only if that grp has that value of course).
Below is the code for my (broken) shiny app:
server <- function(input, output) {
rv <- reactiveValues(
i = NULL,
df = NULL
)
observe({ rv$i <- input$i })
observe({ rv$df <- df[cat == rv$i] })
output$test <- renderUI({
plotList <- lapply( LETTERS[1:6], function(x) plotOutput(x) )
do.call( tagList, unlist(plotList, recursive=FALSE))
})
for(i in LETTERS[1:6]){
local({
my_i <- i
output[[my_i]] <- renderPlot({
if( my_i %in% c('A','D','E')) {
with(rv$df[grp == my_i], plot(x,y, type='l'))
} else {
with(rv$df[grp == my_i], plot(x,y))
}
})
})
}
}
ui <- fluidPage(
titlePanel('Title'),
sidebarLayout(
sidebarPanel(
helpText('Select the Category you would like to view.'),
selectInput('i', 'Category', c('X','Y','Z'), selectize=TRUE)
),
mainPanel(
uiOutput('test')
)
)
)
shinyApp(ui, server)

Answer 1

A reproducible example can be found at the bottom.
A few hints:
1) Using reactive contexts:
In your for Loop at the bottom of the Server Code you are using the reactive variable rv, so you will have to run the Code in a reactive Content. So wrap it in observe().
2) Create a list of Outputs:
If I am not mistaken you used some of the Code in this answer: dynamically add plots to web page using shiny.
It is a good starting Point. For the part of the taglist it might be easier to simplify to:
output$test <- renderUI({
lapply(unique(rv$df$grp), plotOutput)
})
You can also add tagList(), but it is not necessary here,...
3) Correcting the sample data:
You might want to update the df variable:
data.table(cat = rep('Z', 20), grp = rep(LETTERS[4:6], each=10),
x = rep(1:10, times=2), y = rnorm(20) )
Here your have three letters, so you might change it to LETTERS[5:6] or update the other numbers.
Full reproducible example:
library(shiny)
library(data.table)
df <- rbind(
data.table( cat = rep('X', 40), grp = rep(LETTERS[1:4], each=10), x = rep(1:10, times=4), y = rnorm(40) ),
data.table( cat = rep('Y', 30), grp = rep(LETTERS[1:3], each=10), x = rep(1:10, times=3), y = rnorm(30) ),
data.table( cat = rep('Z', 30), grp = rep(LETTERS[4:6], each=10), x = rep(1:10, times=3), y = rnorm(30) )
)
server <- function(input, output) {
rv <- reactiveValues(
i = NULL,
df = NULL
)
observe({ rv$i <- input$i })
observe({ rv$df <- df[cat == rv$i] })
observe({
for(letter in unique(rv$df$grp)){
local({
let <- letter
output[[let]] <- renderPlot({
if( let %in% c('A','D','E')) {
with(rv$df[grp == let], plot(x, y, type='l'))
} else {
with(rv$df[grp == let], plot(x,y))
}
})
})
}
})
output$test <- renderUI({
lapply(unique(rv$df$grp), plotOutput)
})
}
ui <- fluidPage(
titlePanel('Title'),
sidebarLayout(
sidebarPanel(
helpText('Select the Category you would like to view.'),
selectInput('i', 'Category', c('X','Y','Z'), selectize=TRUE)
),
mainPanel(
uiOutput('test')
)
)
)
shinyApp(ui, server)