R ggplot2 click with boxplot - r

Question

When I click one point in the chart, that point is highlighted as red.
But soon it goes back to black.
Is there any way to hold the selection?
library(shiny)
library(ggplot2)
server <- function(input, session, output) {
mtcars$cyl = as.character(mtcars$cyl)
D = reactive({
nearPoints(mtcars, input$click_1,allRows = TRUE)
})
output$plot_1 = renderPlot({
set.seed(123)
ggplot(D(),aes(x=cyl,y=mpg)) +
geom_boxplot(outlier.shape = NA) +
geom_jitter(aes(color=selected_),width=0.02,size=4)+
scale_color_manual(values = c("black","red"),guide=FALSE)
})
output$info = renderPrint({
D()
})
}
ui <- fluidPage(
plotOutput("plot_1",click = clickOpts("click_1")),
verbatimTextOutput("info")
)
shinyApp(ui = ui, server = server)

Answer 1

Okay, my approach is slightly different to Valter's: selected points become red, whilst you can deselect them and they turn back to black.
The key to achieve this effect (or even Valter's answer with 1 selected point) is to use reactiveValues to keep track of the selected points.
library(shiny)
library(ggplot2)
server <- function(input, session, output) {
mtcars$cyl = as.character(mtcars$cyl)
vals <- reactiveValues(clicked = numeric())
observeEvent(input$click_1, {
# Selected point/points
slt <- which(nearPoints(mtcars, input$click_1,allRows = TRUE)$selected)
# If there are nearby points selected:
# add point if it wasn't clicked
# remove point if it was clicked earlier
# Else do nothing
if(length(slt) > 0){
remove <- slt %in% vals$clicked
vals$clicked <- vals$clicked[!vals$clicked %in% slt[remove]]
vals$clicked <- c(vals$clicked, slt[!remove])
}
})
D = reactive({
# If row is selected return "Yes", else return "No"
selected <- ifelse(1:nrow(mtcars) %in% vals$clicked, "Yes", "No")
cbind(mtcars, selected)
})
output$plot_1 = renderPlot({
set.seed(123)
ggplot(D(),aes(x=cyl,y=mpg)) +
geom_boxplot(outlier.shape = NA) +
geom_jitter(aes(color=selected),width=0.02,size=4)+
scale_color_manual(values = c("black","red"),guide=FALSE)
})
output$info = renderPrint({
D()
})
}
ui <- fluidPage(
plotOutput("plot_1",click = clickOpts("click_1")),
verbatimTextOutput("info")
)
shinyApp(ui = ui, server = server)

Answer 2

I am not sure what is the problem but this is the first workaround I have come up to:
library(shiny)
library(ggplot2)
server <- function(input, session, output) {
mtcars$cyl = as.character(mtcars$cyl)
df <- reactiveValues(dfClikced = mtcars)
observe({
if (!is.null(input$click_1)) {
df$dfClikced <- nearPoints(mtcars, input$click_1, allRows = TRUE)
}})
output$plot_1 = renderPlot({
set.seed(123)
if (names(df$dfClikced)[NCOL(df$dfClikced)]== "selected_") {
ggplot(df$dfClikced,aes(x=cyl,y=mpg)) +
geom_boxplot(outlier.shape = NA) +
geom_jitter(aes(color=selected_),width=0.02,size=4)+
scale_color_manual(values = c("black","red"),guide=FALSE)
} else {
ggplot(df$dfClikced,aes(x=cyl,y=mpg)) +
geom_boxplot(outlier.shape = NA) +
geom_jitter(width=0.02,size=4)+
scale_color_manual(values = c("black","red"),guide=FALSE)
}
})
output$info = renderPrint({
df$dfClikced
})
}
ui <- fluidPage(
plotOutput("plot_1",click = clickOpts("click_1")),
verbatimTextOutput("info")
)
shinyApp(ui = ui, server = server)
let me know...