R Shiny unable to display ggplot chart - r

Question

I am having issues displaying ggplot (or any form of charts like hist()). I have tried looking through Stack Overflow but the solutions provided were not useful for this instance. I have not been able to display any of the graphs successfully.
I am using R studio with 3.2.0 build, deploying on Shinyapps.io and viewing via Chrome. I am able to display the graph within R but unable to display it when running with shiny.
Is this a code issue or something I had missed out from my packages? (Note: I have reduced my code trying to troubleshoot, so the variables from ui.R are not used in server.R.)
ui.R
library(shiny)
library(ggplot2)
dataset <- diamonds
diamondcolours <- unique( dataset["color"], incomparables = FALSE)
diamondcolours <- lapply(diamondcolours, as.character)
diamondcuts <- unique( dataset["cut"], incomparables = FALSE)
diamondcuts <- lapply(diamondcuts, as.character)
diamondclarity <- unique( dataset["clarity"], incomparables = FALSE)
diamondclarity <- lapply(diamondclarity, as.character)
carat <- dataset["carat"]
mincarat <- min(carat[ carat != min(carat) ])
# mincarat
maxcarat <- max(carat[ carat != max(carat) ])
# maxcarat
fluidPage(
titlePanel("Diamonds"),
sidebarPanel(
sliderInput('carat', 'Carat', min=mincarat, max=maxcarat,
value=mincarat, step=0.01, round=0),
selectInput('cut', 'Cut', diamondcuts$cut),
selectInput('color', 'Color', diamondcolours$color),
selectInput('clarity', 'Clarity', diamondclarity$clarity)
),
mainPanel(
plotOutput(outputId = 'mainplot')
)
)
server.R
library(shiny)
library(ggplot2)
dataset <- diamonds()
shinyServer(function(input, output, session) {
values <- reactiveValues()
testset <- dataset[ which(dataset$color == values$dcolor & dataset$carat > values$dcarat & dataset$clarity == values$dclarity & dataset$cut== values$dcut ), ]
output$mainplot <- renderPlot({
p <- ggplot(dataset[dataset$price <= 326,], aes(x = carat, y = color))
p <- p + geom_point()
print(p)
} )

Answer 1

Some of the more important problems: (1) data should be reactive to user input, (2) the variable names referring to input are incorrect, (3) all of the code in UI should be in server or, if it's not meant to be reactive, in the global environment. Here is a simplified version that runs,
library(shiny)
library(ggplot2)
dataset(diamonds)
## ** From UI: variables defined here can be seen in the whole app
mincarat <- min(diamonds$carat)
maxcarat <- max(diamonds$carat)
shinyApp(
shinyUI(
fluidPage(
titlePanel("Diamonds"),
sidebarPanel(
sliderInput('dcarat', 'Carat', min=mincarat, max=maxcarat,
value=mincarat, step=0.01, round=0),
selectInput('dcut', 'Cut', levels(diamonds$cut)),
selectInput('dcolor', 'Color', levels(diamonds$color)),
selectInput('dclarity', 'Clarity', levels(diamonds$clarity))
),
mainPanel(
plotOutput('mainplot')
)
)
),
shinyServer(function(input, output) {
## values <- reactiveValues() # unused
## Your data should be reactive - and reference `input`
## to get user-entered values
rxData <- reactive({
dat <- with(diamonds,
diamonds[color == input$dcolor &
carat > input$dcarat &
clarity == input$dclarity &
cut == input$dcut, ])
dat
})
output$mainplot <- renderPlot({
dataset <- rxData() # this is the subsetted data
p <- ggplot(dataset, aes(x = carat, y = price))
p <- p + geom_point()
print(p)
})
})
)

Answer 2

There are number of errors in that code:
You are missing to brackets at the end of the server.R
You are not reading your data correctly
Amended file:
library(shiny)
library(ggplot2)
shinyServer(function(input, output, session) {
data("diamonds")
dataset <- diamonds
rm(diamonds)
values <- reactiveValues()
testset <- dataset[ which(dataset$color == values$dcolor & dataset$carat > values$dcarat & dataset$clarity == values$dclarity & dataset$cut== values$dcut ), ]
output$mainplot <- renderPlot({
p <- ggplot(dataset[dataset$price <= 326,], aes(x = carat, y = color))
p <- p + geom_point()
print(p)
})
})
The ui.R is also wrong. You should put that stuff at the beginning in global.R as per guidelines on scoping rules in Shiny.