Referencing a selected input into a dataset? - r

Question

I am currently having issues with my R.Shiny app which I have designed. The UI has a drop down menu which selects a variable "returnvar", one of the columns in my dataframe source_file. However, upon running the code below I receive an error message stating:
Warning: Unknown or uninitialised column: 'returnvar'.
Warning: Error in : geom_line requires the following missing aesthetics: y
Does anyone know how I can reference an input into my source file? (Something to fix the error from the line source_file_filtered$returnvar) Would greatly appreciate all the help I can get for this, thanks!
App.R
# Defining UI
ui <- fluidPage(theme = shinytheme("darkly"),
navbarPage(
"App", #Title of app
tabPanel("Weekly Cumulative Returns",
sidebarPanel(
tags$h3("Input:"),
dateRangeInput("daterange", "Date range",
start = "2016-01-01",
end = "2021-04-02",
min = "2016-01-01",
max = "2021-04-02",
format = "yyyy/mm/dd",
separator = "to"),
selectInput("returnvar", "Index",
choices= names(source_file[2:(length(source_file)-1)])),
), #sidebarpanel
mainPanel(
# Output: Correlation Plot ----
plotOutput(outputId = "plot2"),
), #mainPanel
) #tabpanel
) #navbarPage
) #fluidPage
# Defining Server
server <- function(input, output) {
#plot for Weekly Cumulative Returns tab
output$plot2 <- renderPlot({
returncolumn(returnvar = input$returnvar,
daterange = input$daterange)
})
}
# Create Shiny Object
shinyApp(ui = ui, server = server)
Global.R
#choose source file to work with
file_name = file.choose()
source_file = read_csv(file_name)
source_file$Date = as.Date(source_file$Date)
#defining returncolumn as a function to return of selected variable over the selected date range in shiny
returncolumn = function(returnvar, daterange)
{
source_file_filtered <- source_file %>%
filter(Date >= daterange[1] & Date <= daterange[2])
g = ggplot(data = source_file_filtered, mapping = aes(x=Date, y=source_file_filtered$returnvar)) + geom_line(color="blue")
print(g)
}

Answer 1

Without the data its hard to test, but changing source_file_filtered$returnvar to source_file_filtered[[returnvar]] should make it work.
returncolumn = function(returnvar, daterange)
{
source_file_filtered <- source_file %>%
filter(Date >= daterange[1] & Date <= daterange[2])
g = ggplot(data = source_file_filtered,
mapping = aes(x = Date,
y = source_file_filtered[[returnvar]])) +
geom_line(color="blue")
print(g)
}