Downloading pdf plot using shiny app after reading excel files - r

Question

As, I am new to shiny apps need some assistance, uploading excel file and generating table output in shiny app works fine, but can't able to download the plot to a pdf format
Here is my code
library(shiny)
library(openxlsx)
library(lattice)
runApp(
list(
ui = fluidPage(
titlePanel("plots"),
sidebarLayout(
sidebarPanel(
fileInput('file1', 'Choose xlsx file',
accept = c(".xlsx")),
tags$hr(),
downloadButton('down',"download plot")
),
mainPanel(
tableOutput('contents'),
plotOutput('plot'))
)
),
server = function(input, output){
output$contents <- renderTable({
inFile <- input$file1
if(is.null(inFile))
return(NULL)
else
read.xlsx(inFile$datapath)
})
plotInput <- reactive({
df <- input$file1
xyplot(df[,2]~df[,1],df(),xlim=c(0,10),ylim=c(0,100),type = "b")
})
output$plot <- renderPlot({
print(plotInput())
})
output$down <- downloadHandler(
filename = function(){paste("plot",".pdf",sep=".") },
content = function(file) {
pdf(file)
xyplot(df[,2]~df[,1],df(),xlim=c(0,10),ylim=c(0,100),type = "b")
dev.off()
}
)
}
)
)

Answer 1

The problem was that in some parts of your code you were accessing a dynamic data frame via df() but you had never defined it.
In this kind of problem, it is best to create a reactive data frame, say, df which contains the uploaded data and is passed to other reactive parts of the code via df().
Full example:
library(shiny)
library(openxlsx)
library(lattice)
runApp(
list(
ui = fluidPage(
titlePanel("plots"),
sidebarLayout(
sidebarPanel(
fileInput('file1', 'Choose xlsx file',
accept = c(".xlsx")),
tags$hr(),
downloadButton('down',"download plot")
),
mainPanel(
tableOutput('contents'),
plotOutput('plot'))
)
),
server = function(input, output){
df <- reactive({
inFile <- input$file1
req(inFile) # require that inFile is available (is not NULL)
# (a user has uploaded data)
# read.xlsx(inFile$datapath)
head(iris, 10)
})
output$contents <- renderTable({
# access uploaded data via df()
df()
})
plotInput <- reactive({
df <- df()
xyplot(df[,2]~df[,1], df ,xlim=c(0,10),ylim=c(0,100),type = "b")
})
output$plot <- renderPlot({
plotInput()
})
output$down <- downloadHandler(
filename = function(){paste("plot",".pdf",sep=".") },
content = function(file) {
pdf(file)
#xyplot(df[,2]~df[,1],df(),xlim=c(0,10),ylim=c(0,100),type = "b")
# you have to print the plot so that you can open pdf file
print(plotInput())
dev.off()
}
)
}
)
)