Download file rshiny - r

Question

I have an rshiny app and i'm trying to download a csv file from the app after it is edited. I followed the examples online, but the download button isn't working. I know the button is fine, its copied directly from the rshiny documentation. I assume the error is server side
server <-function(input,output){# Combine the selected variables into a new data frame
#output$value <- renderPrint({
# str(input$GimmeCSV[2,2])
output$table.preview <- renderTable({
inFile <- input$GimmeCSV
preview <- read.csv(inFile$datapath, header=TRUE, sep=",")
return(head(preview)) # undo Table can be modified
})
output$table.output <- renderTable({
inFile <- input$GimmeCSV
tbl <- read.csv(inFile$datapath, header=TRUE, sep=",")
#return(head(tbl)) # undo Table can be modified
################^ preview of csv table################
#look up how to extract the columns with no name present(something numerical)
#After that is figured out calculating the rest of those values will be a snap
#tbl <- read.csv(inFile$datapath, header=TRUE, sep=",")
#below is temporary file path only used for testing purposes, the above read.csv is the true pooba
#STANDARDS!!!
solar <- tbl$solar
temp <- tbl$temp
ws <- tbl$ws
#return(head(solar))
Ktemp <-temp + 273
ktemp <-temp + 273
#lol
if ((input$Shape) == shape_select[1]){
Len <- (input$diacone)
Height <- (input$hgtcone)
Width <- 0
} else {if((input$Shape) == shape_select[2]){
Len <- (input$diasphere)
Height <- 0
Width <- 0
}
else
Len <- (input$lenprism)
Height <- (input$hgtprism)
Width <- (input$widprism)
}
r <-Len/2
#return(r)
if (Len >=0.037){ # Absorptivity from Luke Miller
Abs <- 0.615
} else {if (Len <= 0.02225 ){Abs <-0.689
} else Abs <- 0.68 }
#works!
Emm <-0.97
#TOTALLY ARBITURARY SURFACE AREA VALUES BASED ON WHAT I KNOW!
ConeA <- (pi*r*r) + (sqrt((Height*Height)+(r*r))) # area of cone
SphereA <- (4*pi*(r*r)) #area of sphere
PrismA <- ((2*Len*Width) + (2*Height*Len) +( 2*Height*Width))
#return(PrismA)
#WORKS
#Deciding which surface area area to calculate
if ((input$Shape) == shape_select[1]){
SA <-ConeA
} else {if((input$Shape) == shape_select[2]){SA <- SphereA}
else SA <-PrismA}
#WOEKS!!!!!!!
#return(SA)
#Temporary placeholder values for PSA
PSA <- SA
SB <- 5.67E-08 # Stephan Boltzman constant
eskyclear <- 0.72 + (0.005*temp)
CC <- 0.5 #Cloud over 0 - 1
esky <- eskyclear + CC*(1 - eskyclear - (8/ktemp)) #IR emissivity from sky
Aradsky <- SA/2 #surface area projected to the sky
Aradground <- SA/2 # surface area projected to the ground
K3 <- esky^(1/4)
K2 <- 4 * SB * Emm * (esky)^(3/4)
K4 <- 4 * SB * Emm
K5 <- 0.6/(0.5*Len)
hc <- 0.6
com1 <- (Abs * solar) + (K2 * (Aradsky/PSA) * K3 * Ktemp^4) + (K4 * (Aradground/PSA) * Ktemp^4) + (K5 * PSA * Ktemp) + (hc*SA*Ktemp) + 2.48*0
com2 <- (4180 * 0) + ((Ktemp^3) * K2 * (Aradsky/PSA)) + (K4 * (Aradground/PSA) *(Ktemp^3)) + (hc*SA) + (K5*PSA)
#works!
Sol <- com1 / com2
modeltemp <- Sol - 273
max <- max(modeltemp)
min <- min(modeltemp)
mydata <- data.frame( Daily_Temp = temp, Solar_Radiation = solar, Body_Temperature = modeltemp, stringsAsFactors = FALSE)
return(mydata)
output$downloadData <- downloadHandler(
filename = function() { paste(input$inFile, '.csv', sep='') },
content = function(file) {
write.csv(mydata, file)
}
)
})
} #app goes here lol
shinyApp(ui, server)
}
Any sugestions are appreciated

Answer 1

I rearranged your code a bit and created 2 reactiveValues at the beginning of the server function.
In an observeEvent, you wait until the fileInput-Button (input$GimmeCSV) is clicked, it reads the csv then and assigns it to the reactive value inputFile. Then you can access this value directly in both renderTable outputs, as you would load the csv twice in your example. If the file is not too big, it shouldnt be a problem, but its not necessary.
The downloadHandler goes outside the renderTable function and takes the input argument (input$inFile), which is used to name the output file. For the content, the second reactiveValue is used, where the data was assigned in output$table.output.
library(shiny)
ui <- fluidPage(
sidebarLayout(
sidebarPanel(
fileInput("GimmeCSV", "Upload a CSV", multiple = F),
textInput("inFile", "Name for Output"),
downloadLink("downloadData", "Download")
),
mainPanel(
tableOutput("table.preview"),
tableOutput("table.output")
)
)
)
server <-function(input,output){
inputFile <- reactiveValues(file = NULL)
outputFile <- reactiveValues(file=NULL)
observeEvent(input$GimmeCSV, {
inFile <- input$GimmeCSV
data <- read.csv(inFile$datapath, header=TRUE, sep=";")
inputFile$file <- data
})
output$table.preview <- renderTable({
head(inputFile$file)
})
output$table.output <- renderTable({
tbl <- inputFile$file
outputFile$file <- tbl
tbl
})
output$downloadData <- downloadHandler(
filename = function() {
paste(input$inFile, '.csv', sep='')
},
content = function(file) {
write.csv(outputFile$file, file)
}
)
}
shinyApp(ui, server)
Hope it helps.