Plotting in Rshiny for newly created variable - r

Question

I have a dataset with categorical data (let's use Arthritis from vcd package for exmaple purposes).
I want to obtain a barplot where for two variables and colouring by a third one.
In base R this would be:
library(vcd)
library(ggplot2)
data(Arthritis)
tab <- as.data.frame(prop.table(table(Arthritis$Treatment, Arthritis$Improved), margin = 1))
ggplot(tab,aes(x=Var1,y=Freq, fill=Var2, label = round(Freq,3)))+
geom_bar(stat = 'identity')+
geom_text(position = position_stack(vjust=0.5))+
scale_fill_manual(values=c('cyan3','tomato', 'blue'), guide = guide_legend(reverse=TRUE))
Which would give the result:
In my shinyApp the user should be able to choose the variables to plot.
For this I've created:
# Shiny
library(shiny)
library(shinyWidgets)
library(shinyjqui)
library(shinyjs)
# Data
library(readxl)
library(dplyr)
library(vcd)
# Plots
library(ggplot2)
not_sel <- "Not Selected"
ui <- navbarPage(
title = "Plotter",
windowTitle = "Plotter",
tabPanel(
"Plotter",
fluidPage(
fluidRow(
sidebarPanel(
title = "Inputs",
fileInput("xlsx_input", "Select XLSX file to import", accept = c(".xlsx")),
selectInput("num_var_1", "Variable X axis", choices = c(not_sel)),
selectInput("num_var_2", "Variable Y axis", choices = c(not_sel)),
uiOutput("factor"),
br(),
actionButton("run_button", "Run Analysis", icon = icon("play"))
),
# Main panel
mainPanel(
tabsetPanel(
tabPanel(
"Plot",
br(),
plotOutput("plot_1"),
br(),
verbatimTextOutput("data")
)
)
)
)
)
)
)
################# --------------------------------------------------------------
# Server
################# --------------------------------------------------------------
server <- function(input, output){
# Dynamic selection of the data
data_input <- reactive({
#req(input$xlsx_input)
#inFile <- input$xlsx_input
#read_excel(inFile$datapath, 1)
Arthritis
})
# We update the choices available for each of the variables
observeEvent(data_input(),{
choices <- c(not_sel, names(data_input()))
updateSelectInput(inputId = "num_var_1", choices = choices)
updateSelectInput(inputId = "num_var_2", choices = choices)
})
num_var_1 <- eventReactive(input$run_button, input$num_var_1)
num_var_2 <- eventReactive(input$run_button, input$num_var_2)
# data
data_discrete_plot <- reactive({
req(data_input(), input$num_var_1, input$num_var_2)
df <- data_input()
df1 <- as.data.frame(prop.table(table(df[[input$num_var_1]], df[[input$num_var_2]]), margin = 1))
df1
})
# Function for printing the plots
draw_barplot <- function(data_input)
ggplot(data = data_input, aes(x=data_input[1], y=data_input[3], fill=data_input [2], label = round(Freq, 3))) +
geom_bar(stat = "identity") +
scale_fill_manual(guide = guide_legend(reverse=TRUE)) +
ylim(0, 100) +
theme_bw()
## BarPlot -------------------------------------------------------------------
plot_1 <- eventReactive(input$run_button,{
req(data_input())
draw_barplot(data_discrete_plot())
})
output$plot_1 <- renderPlot(plot_1())
output$data <- renderPrint(data_discrete_plot())
}
# Connection for the shinyApp
shinyApp(ui = ui, server = server)
As you can see in the previous RepEx we are obtaining the contingency table, however, I'm finding some trouble when calling for the variables to plot,
as it is a new dataframe with different names for the data.
If I run the code above, I get an error that says: default method not implemented for type 'list'
But if I try to do something like:
data_input[1] <- unlist(data_input[1])
data_input[2] <- unlist(data_input[2])
data_input[3] <- unlist(data_input[3])
The application crashes.

Answer 1

As the columns of your new dataframe have names Var1, Var2 and Freqyou could do:
draw_barplot <- function(data_input) {
ggplot(data = data_input, aes(x = Var1, y = Freq, fill = Var2, label = round(Freq, 3))) +
geom_bar(stat = "identity") +
scale_fill_discrete(guide = guide_legend(reverse = TRUE)) +
ylim(0, 1) +
theme_bw()
}
Additionally I replaced scale_fill_manual by scale_fill_discrete as for the first one you have to provide a vector of color values and set ylim(0, 1) as the proportions in the ´Freq` column are on a 0 to 1 scale.