问题
I am relying on the code chunk found here to create a Shiny app to upload a table, edit the table, then download the table. I have managed to edit a table that is already loaded in memory (iris) but how do I edit a table that is to be uploaded in Shiny?.
I have tried the code in the link above and verified that it works. I have also tried the code below and this works too. What I have not been able to achieve is to convert the data frame x into a reactive object that is assigned to an uploaded file, and edit all the references to x accordingly.
# This code works, but lacks a fileinput object
# and needs to be amended for a reactive dataframe...
library(shiny)
library(DT)
shinyApp(
ui = fluidPage(
fluidRow(
# ~~ add fileInput("file1", "Choose file") here ~~
downloadButton("download")
),
fluidRow(
DT::dataTableOutput('x1')
)
),
server = function(input, output, session) {
# Do I make x reactive?
x = iris
x$Date = Sys.time() + seq_len(nrow(x))
output$x1 = DT::renderDataTable(x, selection = 'none', rownames = FALSE, edit = TRUE)
proxy = dataTableProxy('x1')
observeEvent(input$x1_cell_edit, {
info = input$x1_cell_edit
str(info)
i = info$row
j = info$col + 1
v = info$value
x[i, j] <<- DT:::coerceValue(v, x[i, j])
replaceData(proxy, x, resetPaging = FALSE, rownames = FALSE)
})
output$download <- downloadHandler("example.csv",
content = function(file){
write.csv(x, file)
},
contentType = "text/csv")
}
)
Previous attempts at this have thrown errors, mostly to do with operations not being allowed without an active reactive context.
The code below shows what I want to achieve, but throws an error: "argument "expr" is missing, with no default"
library(shiny)
library(DT)
shinyApp(
ui = fluidPage(
fluidRow(
fileInput("upload", "Choose CSV File",
multiple = FALSE,
accept = c("text/csv",
"text/comma-separated-values,text/plain",
".csv")),
downloadButton("download")
),
fluidRow(
DT::dataTableOutput('x1')
)
),
server = function(input, output, session) {
#x = iris
# In this edited example x is now a reactive expression, dependent on input$upload
x <- eventReactive({
# input$file1 will be NULL initially. After the user selects
# and uploads a file, head of that data file by default,
# or all rows if selected, will be shown.
req(input$upload)
# when reading semicolon separated files,
# having a comma separator causes `read.csv` to error
tryCatch(
{
x <- read.csv(input$upload$datapath,
header = TRUE,
sep = ",",
stringsAsFactors = TRUE,
row.names = NULL)
},
error = function(e) {
# return a safeError if a parsing error occurs
stop(safeError(e))
}
)
})
#x$Date = Sys.time() + seq_len(nrow(x))
output$x1 = DT::renderDataTable(x(), selection = 'none', rownames = FALSE, edit = TRUE)
proxy = dataTableProxy('x1')
observeEvent(input$x1_cell_edit, {
info = input$x1_cell_edit
str(info)
i = info$row
j = info$col + 1
v = info$value
x()[[i, j]] <<- DT:::coerceValue(v, x()[[i, j]])
newdf <- x()
replaceData(proxy, newdf, resetPaging = FALSE, rownames = FALSE)
})
output$download <- downloadHandler("example.csv",
content = function(file){
write.csv(x(), file)
},
contentType = "text/csv")
}
)
回答1:
See ?eventReactive.
You should do:
x <- eventReactive(input$upload, { # 'input$upload' was the "expr missing"
......
or
x <- reactive({
req(input$upload)
......
回答2:
With thanks to Stephane, and inspiration from this related question, I think I have an answer.
Key is to use reactiveValues as a workaround to DT:::coerceValue not liking reactive expressions. I've included a verbatimTextOutput to illustrate the stored changes to the table after you edit the data table. The download button allows you to download the edited table too.
library(shiny)
library(DT)
shinyApp(
ui = fluidPage(
fluidRow(
fileInput("upload", "Choose CSV File",
multiple = FALSE,
accept = c("text/csv",
"text/comma-separated-values,text/plain",
".csv")),
downloadButton("download")
),
fluidRow(
DT::dataTableOutput('x1'),
verbatimTextOutput("print")
)
),
server = function(input, output, session) {
# In this edited example x is now a reactive expression, dependent on input$upload
# Key to the solution is the use of reactiveValues, stored as vals
vals <- reactiveValues(x = NULL)
observe({
# input$upload will be NULL initially. After the user selects
# and uploads a file, head of that data file by default,
# or all rows if selected, will be shown.
req(input$upload)
# when reading semicolon separated files,
# having a comma separator causes `read.csv` to error
tryCatch(
{
x <- read.csv(input$upload$datapath,
header = TRUE,
sep = ",",
stringsAsFactors = TRUE,
row.names = NULL)
},
error = function(e) {
# return a safeError if a parsing error occurs
stop(safeError(e))
}
)
# Reactive values updated from x
vals$x <- x
})
output$print <- renderPrint({
vals$x
})
output$x1 = DT::renderDataTable(vals$x, selection = 'none', rownames = FALSE, edit = TRUE)
proxy = dataTableProxy('x1')
observeEvent(input$x1_cell_edit, {
info = input$x1_cell_edit
str(info)
i = info$row
j = info$col + 1
v = info$value
# Below is the crucial spot where the reactive value is used where a reactive expression cannot be used
vals$x[i, j] <<- DT:::coerceValue(v, vals$x[i, j])
replaceData(proxy, vals$x, resetPaging = FALSE, rownames = FALSE)
})
output$download <- downloadHandler("example.csv",
content = function(file){
write.csv(vals$x, file, row.names = F)
},
contentType = "text/csv")
}
)
来源：https://stackoverflow.com/questions/54426548/how-to-edit-a-table-using-dt-and-shiny-from-an-uploaded-file