How to use a reactive variable in server Shiny - r

Question

I would like to create an application such as below, only at the beginning is to choose the number of cylinders. The following example selects a database, I would like to give up and go straight to the selection of cylinders. Can I use the filter option here?
My idea:
df_mtcars <- reactive({
cylinder_selected <- as.numeric(input$si_cylinders[1])
df <- mtcars %>% filter(cyl == cylinder_selected)
return(df)
})
My code:
ui:
library(radarchart)
shinyUI(pageWithSidebar(
headerPanel("Car Comparison Radar"),
sidebarPanel(
uiOutput("choose_dataset"),
uiOutput("choose_car"),
uiOutput("choose_columns")
),
mainPanel(
chartJSRadarOutput('radar', height = '350px')
)
))
server:
library(shiny)
library(radarchart)
shinyServer(function(input, output) {
# choose dataset but I want choose cyl
output$choose_dataset <- renderUI({
data_sets <- "mtcars"
selectInput("dataset", "Data set", data_sets)
})
# select a car
output$choose_car <- renderUI({
selectInput("car","car",as.list(rownames(get(input$dataset))))
})
# Check boxes
output$choose_columns <- renderUI({
# If missing input, return to avoid error later in function
if(is.null(input$dataset))
return()
# Get the data set with the appropriate name
dat <- get(input$dataset)
colnames <- names(dat)
# Create the checkboxes and select them all by default
checkboxGroupInput("columns", "Choose columns",
choices = colnames,
selected = colnames)
})
output$radar <- renderChartJSRadar({
# Get the data set
dat <- get(input$dataset)
# Make sure columns are correct for data set (when data set changes, the
# columns will initially be for the previous data set)
if (is.null(input$columns) || !(input$columns %in% names(dat)))
return()
# Keep the selected columns
dat <- dat[, input$columns, drop = FALSE]
#reform data for plot
dat <- as.data.frame(t(dat), stringsAsFactors = FALSE)
dat$labs <- row.names(dat)
dat <- dat[, c('labs', input$car)]
chartJSRadar(dat)
})
})

Answer 1

As it is uiOutput("choose_car") gives you all car possibilities. If you add a selectInputfor selection of cylinders you will have a problem, because you have some specific cars for each cylinder numbers.
So you could have your selectInputfor cars conditional on selectInputfor cylinders.
You can remove uiOutput("choose_dataset") on your own so based on your example you could try this:
ui = pageWithSidebar(
headerPanel("Car Comparison Radar"),
sidebarPanel(
uiOutput("choose_dataset"),
uiOutput("choose_cyclinder"),
uiOutput("choose_car"),
uiOutput("choose_columns")
),
mainPanel(
chartJSRadarOutput('radar', height = '350px')
)
)
server = function(input, output) {
output$choose_cyclinder <- renderUI({
temp <- mtcars %>% group_by(cyl) %>% summarise(Counts = n())
cyl <- levels(as.factor(temp$cyl))
selectInput("select_cyl", "Choose a cylinder", as.list(cyl), selected=TRUE, multiple = FALSE)
})
# choose dataset but I want choose cyl
output$choose_dataset <- renderUI({
data_sets <- "mtcars"
selectInput("dataset", "Data set", data_sets)
})
# select a car
output$choose_car <- renderUI({
dat <- get(input$dataset)
dat <- dat %>% tibble::rownames_to_column('carnames') %>%
filter(cyl %in% c(input$select_cyl)) %>%
tibble::column_to_rownames('carnames')
selectInput("car","car",as.list(rownames(dat)))
})
# Check boxes
output$choose_columns <- renderUI({
# If missing input, return to avoid error later in function
if(is.null(input$dataset))
return()
# Get the data set with the appropriate name
dat <- get(input$dataset)
colnames <- names(dat)
# Create the checkboxes and select them all by default
checkboxGroupInput("columns", "Choose columns",
choices = colnames,
selected = colnames)
})
output$radar <- renderChartJSRadar({
# Get the data set
dat <- get(input$dataset)
# dat <- mtcars
# Make sure columns are correct for data set (when data set changes, the
# columns will initially be for the previous data set)
if (is.null(input$columns) || !(input$columns %in% names(dat)))
return()
# Keep the selected columns
dat <- dat[, input$columns, drop = FALSE]
# dat <- dat %>% filter(cyl %in% c(input$select_cyl))
#reform data for plot
dat <- as.data.frame(t(dat), stringsAsFactors = FALSE)
dat$labs <- row.names(dat)
dat <- dat[, c('labs', input$car)]
chartJSRadar(dat)
})
}
shinyApp(ui, server)
EDIT:
ui = pageWithSidebar(
headerPanel("Car Comparison Radar"),
sidebarPanel(
#uiOutput("choose_dataset"),
uiOutput("choose_cyclinder"),
uiOutput("choose_car"),
uiOutput("choose_columns")
),
mainPanel(
chartJSRadarOutput('radar', height = '350px')
)
)
server = function(input, output) {
output$choose_cyclinder <- renderUI({
temp <- mtcars %>% group_by(cyl) %>% summarise(Counts = n())
cyl <- levels(as.factor(temp$cyl))
selectInput("select_cyl", "Choose a cylinder", as.list(cyl), selected=TRUE, multiple = FALSE)
})
# choose dataset but I want choose cyl
# output$choose_dataset <- renderUI({
# data_sets <- "mtcars"
# selectInput("dataset", "Data set", data_sets)
# })
# select a car
output$choose_car <- renderUI({
# dat <- get(mtcars)
dat <- mtcars
dat <- dat %>% tibble::rownames_to_column('carnames') %>%
filter(cyl %in% c(input$select_cyl)) %>%
tibble::column_to_rownames('carnames')
selectInput("car","car",as.list(rownames(dat)))
})
# Check boxes
output$choose_columns <- renderUI({
# If missing input, return to avoid error later in function
# if(is.null(input$dataset))
# return()
# Get the data set with the appropriate name
# dat <- get(input$dataset)
dat <- mtcars
colnames <- names(dat)
# Create the checkboxes and select them all by default
checkboxGroupInput("columns", "Choose columns",
choices = colnames,
selected = colnames)
})
output$radar <- renderChartJSRadar({
# Get the data set
#dat <- get(input$dataset)
dat <- mtcars
# Make sure columns are correct for data set (when data set changes, the
# columns will initially be for the previous data set)
if (is.null(input$columns) || !(input$columns %in% names(dat)))
return()
# Keep the selected columns
dat <- dat[, input$columns, drop = FALSE]
# dat <- dat %>% filter(cyl %in% c(input$select_cyl))
#reform data for plot
dat <- as.data.frame(t(dat), stringsAsFactors = FALSE)
dat$labs <- row.names(dat)
dat <- dat[, c('labs', input$car)]
chartJSRadar(dat)
})
}
shinyApp(ui, server)