using drop down bottom in shiny to loaed files from a folder - r

Question

I am using shiny to upload different data files from a certain folder and plot a histogram based on a certain column. The name of each file looks like "30092017ARB.csv" (date + ARB.csv).
The code loops over all file names in the data-folder and print the name of files in a drop-down bottom. After selecting the name of file it should be uploaded and plot a histogram of the mw-column (the name of column is "mw). My GUI looks as follows:
library("shiny")
dataset <- list.files("C:/R_myfirstT/data", pattern=".*.csv$")
# Define UI for dataset viewer app ----
ui <- fluidPage(
# App title ----
titlePanel("Data plot"),
# Sidebar layout with input and output definitions ----
sidebarLayout(
# Sidebar panel for inputs ----
sidebarPanel(
# Input: Selector for choosing dataset ----
selectInput(inputId = "date",
label = "Choose a date:",
choices = dataset)
),
# Main panel for displaying outputs ----
mainPanel(
plotOutput("plot")
)
)
)
and the server
# Define server ----
dataset <- list.files("C:/R_myfirstT/data", pattern=".*.csv$")
dat.name<-paste("C:/R_myfirstT/data/",dataset,sep = "")
server <- function(input, output) {
datasetInput <- reactive({
switch(input$dataset,
for (i in 1:length(dataset)){
toString(dataset[i])=read.csv(file=dat.name[i], header=TRUE, sep=";")
}
)
output$plot <- renderPlot({
hist(dataset.mw, breaks = 40)
})
})
}
My problem is: I do not get any histogram! I get just the which is nice however, not entirely my goal!
Any idea what could be the reason?

Answer 1

Something like this works:
ui.R
library("shiny")
# Define UI for dataset viewer app ----
ui <- fluidPage(
# App title ----
titlePanel("Data plot"),
# Sidebar layout with input and output definitions ----
sidebarLayout(
# Sidebar panel for inputs ----
sidebarPanel(
# Input: Selector for choosing dataset ----
selectInput(inputId = 'date',
label = 'Choose a date:',
choices = list.files(path = "./data",
full.names = FALSE,
recursive = FALSE))
),
# Main panel for displaying outputs ----
mainPanel(
plotOutput("plot")
)
)
)
server.R
# Define server ----
server <- function(input, output) {
dataset <- reactive({
infile <- input$date
if (is.null(infile)){
return(NULL)
}
read.csv(paste0('./data/',infile))
})
output$plot <- renderPlot({
x <- dataset()[,1]
hist(x, breaks = 40)
})
}