R Shiny: Read CSV and save in a variable with dplyr and ggplot

I'm trying to add a fileInput into my R Shiny program that users can add their own CSV/Excel files into, however, I'm running into some issues.

If I run the code reading the CSV directly from my PC (no fileInput) I have no problem, but anytime I try to input it I get errors.

I've done some research and tried to copy what I've seen online, but their solutions are not working for me. I've seen this post and this post already, but their methods are not working for. Or I'm still doing something wrong.

ui <- fluidPage(

theme = 'custom.css',

dashboardPage(
dashboardHeader(title = 'Student Grades'),
dashboardSidebar(
fileInput(inputId = 'file', label = 'Select a file...'),
selectInput(inputId = 'periodVar',
label = 'Select Period',
choices = unique(grades$Period)),
uiOutput('secondSelection'),
dataTableOutput('individualSummary'),
img(src='lhimg.JPG', width = '100%')
),

dashboardBody(
useShinyjs(),
tabsetPanel(
tabPanel(
'Test',
tableOutput('contents')
),
tabPanel(
'Graph',
plotOutput('individualGraph')
)
)
)
)
)

server <- function(input, output, session) {

# grades <- eventReactive(input$file,
# read.csv(input$file$datapath)
# )

grades2 <- reactive(
inFile <- input$file
if (is.null(inFile))
return(NULL)
myTbl <- read.csv(inFile$datapath)
return(myTbl)
)

# observe(
# grades2 = input$file
# if (is.null(file))
# return(NULL)
#
# grades2 = read.csv(grades2$datapath)
# )

tidyGrades <- function(data)
data %>%
gather(key = Type, value = Grade, (c('Test', 'Quiz', 'Homework')), na.rm = T) %>%
arrange(Period, Student,Date, Type) %>%
mutate(Weight = ifelse(Type == 'Homework', 30,
ifelse(Type == 'Quiz', 20, 50)),
Date = mdy(Date))


weightedMeanDf <- tidyGrades(grades2)


There is a small snippet of my code. I can post the entire thing if needed, but I don't want to make it difficult to read while trying to get help. The weightedMeanDf is just one thing I need to do, but I have a handful of other plots and tables that I need to generate as well. The commented codes are the different things I've tried based off solutions online. The closest I got was using the uncommented code (first reactive) function inside the server function.

But I get this error with it:

Error in UseMethod("gather_") :
no applicable method for 'gather_' applied to an object of class "c('reactiveExpr', 'reactive')"


I'm really at a loss and now I'm running out of ideas. Maybe I'm going about it entirely the wrong way. Maybe the best way is to use a reactive function for every plot and data frame created? I feel like that would just slow everything down as opposed to reading the csv file once, then generating graphs and plots based off the first reading?

grades2

grades2()

weightedMeanDf

weightedMeanDf <- reactive( tidyGrades(grades2()) )

1 Answer
1

How about this???

library(shiny)
library(digest)

# Create data to read
write.csv(file="~/iris.csv",iris)

shinyApp(ui=shinyUI(
fluidPage(
sidebarLayout(
sidebarPanel(
textInput("path","Enter path: "),
actionButton("readFile","Read File"),
tags$hr()
),
mainPanel(
tableOutput('contents')
)))
),
server = shinyServer(function(input,output,session)
file <- reactiveValues(path=NULL,md5=NULL,rendered=FALSE)

# Read file once button is pressed
observeEvent(input$readFile,
if ( !file.exists(input$path) )
print("No such file")
return(NULL)

tryCatch(
read.csv(input$path)
file$path <- input$path
file$md5 <- digest(file$path,algo="md5",file=TRUE)
file$rendered <- FALSE
,
error = function(e) print(paste0('Error: ',e)) )
)

observe(
invalidateLater(1000,session)
print('check')

if (is.null(file$path)) return(NULL)

f <- read.csv(file$path)
# Calculate ckeksum
md5 <- digest(file$path,algo="md5",file=TRUE)

# If no change in cheksum, do nothing
if (file$md5 == md5 && file$rendered == TRUE) return(NULL)

output$contents <- renderTable(

print('render')
file$rendered <- TRUE
f
)
)

))


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