dealing with an input dataset in R Shiny - r

Question

I'm new to R-Shiny and my question might be very simple. After hours of thinking and searching, I couldn't solve the issue. Here is the problem:
1) My app asks user to upload his dataset.
2) Then in the server file, I read the dataset and I did some analyses and I report back the results into the user interface.
3)My user interface has 4 different out puts.
4) I read the dataset in the "render" function of each output. ISSUE: by doing so, the data is locally defined in the scope of each function which means that I need to read it over again for each output.
5) This is very in-efficient, Is there any alternative? using reactive ?
6) Below is a sample code showing how I wrote my server.R:
shinyServer(function(input, output) {
# Interactive UI's:
# %Completion
output$myPlot1 <- renderPlot({
inFile <- input$file
if (is.null(inFile)) return(NULL)
data <- read.csv(inFile$datapath, header = TRUE)
# I use the data and generate a plot here
})
output$myPlot2 <- renderPlot({
inFile <- input$file
if (is.null(inFile)) return(NULL)
data <- read.csv(inFile$datapath, header = TRUE)
# I use the data and generate a plot here
})
})
How can I just get the input data once and just use the data in my output functions ?
Thanks very much,

Answer 1

You can call the data from the file in a reactive function. It can then be accessed for example as
myData() in other reactive functions:
library(shiny)
write.csv(data.frame(a = 1:10, b = letters[1:10]), 'test.csv')
runApp(list(ui = fluidPage(
titlePanel("Uploading Files"),
sidebarLayout(
sidebarPanel(
fileInput('file1', 'Choose CSV File',
accept=c('text/csv',
'text/comma-separated-values,text/plain',
'.csv'))
),
mainPanel(
tableOutput('contents')
)
)
)
, server = function(input, output, session){
myData <- reactive({
inFile <- input$file1
if (is.null(inFile)) return(NULL)
data <- read.csv(inFile$datapath, header = TRUE)
data
})
output$contents <- renderTable({
myData()
})
}
)
)