Define column values as input for reactive shiny plot - r

Question

I want to start a shiny app for practice where a use can choose from a dropdown the values in the "cut" column from the diamonds dataset (from ggplot2).
My ui looks as following:
library(shiny)
# Define UI for application that draws a histogram
shinyUI(fluidPage(
# Application title
titlePanel("Reactive Boxplot"),
# Show a boxplot of the selected cut
mainPanel(
selectInput("column", label = h3("Column to plot"),
choices = c("", diamonds$cut),
selected = 1,
width='55%',
multiple = FALSE),
plotOutput("diamondshist")
)
)
)
I don't know how to define the input variables as the five distinct values in the "cut" column of diamonds dataset. Any input on this?
My server file looks like shared below. I assume I would also need to adapt the input data for the plot.
library(shiny)
library(ggplot2)
# Define server logic required to draw a histogram
shinyServer(function(input, output) {
compute_plot <- reactive({
if (input$column != ""){
ggplot(diamonds[, input$column])+
labs(title = "From diamonds dataset")+
geom_boxplot(aes(x = cut, y = price))+
scale_y_reverse()
}
})
output$diamondshist <- renderPlot({
compute_plot();
})
})

Answer 1

I assume this is what you are after:
pass the levels of diamonds$cut as input selection
subset the diamonds dataset to the selected cut
library(shiny)
library(ggplot2)
# Define UI for application that draws a histogram
ui=shinyUI(fluidPage(
# Application title
titlePanel("Reactive Boxplot"),
# Show a boxplot of the selected cut
mainPanel(
selectInput("column", label = h3("Column to plot"),
choices = c("", levels(diamonds$cut)),
selected = NULL,
width='55%',
multiple = FALSE),
plotOutput("diamondshist")
)
)
)
# Define server logic required to draw a histogram
server=shinyServer(function(input, output) {
compute_plot <- reactive({
if (input$column != ""){
ggplot(subset(diamonds, cut==input$column))+
labs(title = "From diamonds dataset")+
geom_boxplot(aes(x = cut, y = price))+
scale_y_reverse()
}
})
output$diamondshist <- renderPlot({
compute_plot();
})
})
shinyApp(ui = ui, server = server)