Shiny if else statement - r

Question

I am having problems using conditional statements in Shiny. I want the user select number of variable. If choose 1 variable then plot chart of 1 variable (ex density plot), if choose 2 variable then plot chart of 2 variables (ex scatter plot). I have tried a few ways, but the output is not as my expected. How can i use if else statement in Shiny server? Tks
UI
df <- mtcars
ui <- fluidPage(
h1("My first app",
style = 'color: green;
font-style: italic'),
hr(),
fluidRow(
sidebarPanel(
radioButtons(inputId = "number",
label = "Select number of variable",
choices = c("1 variable" = 1,
"2 variable" = 2)),
selectInput(inputId = "x",
label = "Variable 1",
choices = names(df)),
conditionalPanel(
condition = "input.number == 2",
selectInput(inputId = "y",
label = "Variable 2",
choices = names(df))
)
),
column(8, plotOutput("plot"))
),
hr(),
plotOutput("plot") )
Server
server <- function(input, output, session){
observeEvent(input$x,
{updateSelectInput(session,
inputId = "y",
label = "Variable 2",
choices = names(df)[names(df) != input$x])
})
data <- reactive({
if(input$number == 1){
data <- df %>%
select(input$x)
} else {
data <- df %>%
select(input$x, input$y)
}
})
output$plot <- renderPlot({
if(input$number == 1){
ggplot(data = data(),
x = get(input$x))+
geom_density()
} else {
ggplot(data = data,
x = get(input$x),
y = get(input$y)) +
geom_point()
}
})
}
shinyApp(ui = ui, server = server)

Answer 1

You can try the following code -
plotOutput("plot") was mentioned twice, removed it to include it only once.
We don't need to check for conditions while creating the dataset in reactive, handle it in the plot code itself.
Use .data to refer column names in ggplot code.
library(shiny)
library(ggplot2)
df <- mtcars
ui <- fluidPage(
h1("My first app",
style = 'color: green;
font-style: italic'),
hr(),
fluidRow(
sidebarPanel(
radioButtons(inputId = "number",
label = "Select number of variable",
choices = c("1 variable" = 1,
"2 variable" = 2)),
selectInput(inputId = "x",
label = "Variable 1",
choices = names(df)),
conditionalPanel(
condition = "input.number == 2",
selectInput(inputId = "y",
label = "Variable 2",
choices = names(df))
)
),
column(8, plotOutput("plot"))
)
)
server <- function(input, output, session){
data <- reactive({
df
})
observeEvent(input$x,
{updateSelectInput(session,
inputId = "y",
label = "Variable 2",
choices = names(df)[names(df) != input$x])
})
output$plot <- renderPlot({
if(input$number == 1){
plot <- ggplot(data = data(), aes(x = .data[[input$x]])) + geom_density()
} else {
plot <- ggplot(data = data(),
aes(x = .data[[input$x]], y = .data[[input$y]])) +
geom_point()
}
plot
})
}
shinyApp(ui = ui, server = server)

Answer 2

You could use aes_string.
Another very important point is never to use the same output twice in UI:
df <- mtcars
library(ggplot2)
library(dplyr)
ui <- fluidPage(
h1("My first app",
style = 'color: green;
font-style: italic'),
hr(),
fluidRow(
sidebarPanel(
radioButtons(inputId = "number",
label = "Select number of variable",
choices = c("1 variable" = 1,
"2 variable" = 2)),
selectInput(inputId = "x",
label = "Variable 1",
choices = names(df)),
conditionalPanel(
condition = "input.number == 2",
selectInput(inputId = "y",
label = "Variable 2",
choices = names(df))
)
),
column(8, plotOutput("plot"))
),
hr()
# Never use output twice : the UI won't work!
#plotOutput("plot")
)
server <- function(input, output, session){
observeEvent(input$x,
{updateSelectInput(session,
inputId = "y",
label = "Variable 2",
choices = names(df)[names(df) != input$x])
})
data <- reactive({
if(input$number == 1){
data <- df %>%
select(input$x)
} else {
data <- df %>%
select(input$x, input$y)
}
})
output$plot <- renderPlot({
cat(input$x)
if(input$number == 1){
ggplot(data = data())+
geom_density(aes_string(x=input$x))
} else {
ggplot(data = data()) +
geom_point(aes_string(x=input$x,y=input$y))
}
})
}
shinyApp(ui = ui, server = server)