Select current plot and download to file - r

Question

How can I save the current plot that is displayed on the mainPanel? I am having trouble pointing the correct graphic to the download Handler. This is what I have:
library(shiny)
library(ggplot2)
library(tidyverse)
library(shinythemes)
library(plotly)
library(scales)
library(shinyWidgets)
library(shinydashboard)
library(shinyjs)
# Define input choices
type <- c("first", "second")
#Data for lambda
table <- structure(list(year = 1991:2010, lambda = c(0.68854, 0.75545,
1.63359, 1.22282, 1.70744, 1.09692, 0.51159, 1.3904, 1.09132,
0.59846, 0.43055, 0.80135, 0.69027, 0.65646, 0.95485, 1.04818,
0.67859, 1.00461, 1.16665, 1.28203)), row.names = c(NA, -20L), class = "data.frame")
ui <- fluidPage(
useShinyjs(), # to initialise shinyjs
navbarPage("Test",
windowTitle = "A Test",
sidebarPanel(
h3(""),
#Dropdown to select the desired kind of graphic
selectInput(inputId = "graphtype",
label = "Graphic",
choices = type,
selected = "first"),
disabled( #start as disabled
checkboxInput("Fixed","Fixed Y axes", FALSE))),
downloadButton('downloadPlot', 'Download Plot'),
#Graphic Area mainPanel. Graphic on top and table right below it
mainPanel(plotOutput("plot"),
dataTableOutput("mytable"))
))
###################################################################################################
server<- function (input, output, session) {
session$onSessionEnded(function() {
stopApp()
})
#Plot data
output$plot <- renderPlot({
xlabels <- 1991:2011
switch(input$graphtype,
"first" = {
disable("Fixed")
print(ggplot(table,aes(year,lambda)) + geom_line(size=1.5,colour="blue") + geom_point(colour="orange",size=4) +
scale_x_continuous("",breaks = xlabels) +
theme(axis.text.x = element_text(angle = 45, vjust = 0.5)) +
labs(x="",y="test",title= paste0("Population growth rate of Fish ")))
},
{
enable("Fixed")
if(input$Fixed == FALSE){
"second" <- print(ggplot(table,aes(year,lambda)) + geom_line(size=1.5,colour="red") + geom_point(colour="green",size=4) +
scale_x_continuous("",breaks = xlabels) +
theme(axis.text.x = element_text(angle = 45, vjust = 0.5)) +
labs(x="",y="fish test",title= paste0("Population growth")))
}
else{
"second" <- print(ggplot(table,aes(year,lambda)) + geom_line(size=1.5,colour="yellow") + geom_point(colour="green",size=4) +
scale_x_continuous("",breaks = xlabels) +
theme(axis.text.x = element_text(angle = 45, vjust = 0.5)) +
labs(x="",y="fish test",title= paste0("Population growth")))
}
}
)
output$downloadPlot <- downloadHandler(
filename = "plot.png" ,
content = function(file) {
ggsave(plot(), filename = file)
})
})
}
shinyApp(ui = ui, server = server)

Answer 1

One option would be to move your plotting code to a reactive. This way you could print your plot inside renderPlot but also pass the plot to the ggsave inside the downloadHandler. Additionally I cleaned up the code to switch between the plots a little bit.
Note: I moved the download button to the sidebar because otherwise it would not work. Also, I made the code more minimal by removing all the unnecessary packages and code.
library(shiny)
library(ggplot2)
# Define input choices
type <- c("first", "second")
# Data for lambda
table <- structure(list(year = 1991:2010, lambda = c(
0.68854, 0.75545,
1.63359, 1.22282, 1.70744, 1.09692, 0.51159, 1.3904, 1.09132,
0.59846, 0.43055, 0.80135, 0.69027, 0.65646, 0.95485, 1.04818,
0.67859, 1.00461, 1.16665, 1.28203
)), row.names = c(NA, -20L), class = "data.frame")
ui <- fluidPage(
sidebarPanel(
h3(""),
# Dropdown to select the desired kind of graphic
selectInput(
inputId = "graphtype",
label = "Graphic",
choices = type,
selected = "first"
),
checkboxInput("Fixed", "Fixed Y axes", FALSE),
downloadButton("downloadPlot", "Download Plot")
),
# Graphic Area mainPanel. Graphic on top and table right below it
mainPanel(
plotOutput("plot"),
dataTableOutput("mytable")
)
)
###################################################################################################
server <- function(input, output, session) {
session$onSessionEnded(function() {
stopApp()
})
# Plot data
create_plot <- reactive({
xlabels <- 1991:2011
if (input$graphtype == "first") {
ggplot(table, aes(year, lambda)) +
geom_line(size = 1.5, colour = "blue") +
geom_point(colour = "orange", size = 4) +
scale_x_continuous("", breaks = xlabels) +
theme(axis.text.x = element_text(angle = 45, vjust = 0.5)) +
labs(x = "", y = "test", title = paste0("Population growth rate of Fish "))
} else {
if (!input$Fixed) {
ggplot(table, aes(year, lambda)) +
geom_line(size = 1.5, colour = "red") +
geom_point(colour = "green", size = 4) +
scale_x_continuous("", breaks = xlabels) +
theme(axis.text.x = element_text(angle = 45, vjust = 0.5)) +
labs(x = "", y = "fish test", title = paste0("Population growth"))
} else {
ggplot(table, aes(year, lambda)) +
geom_line(size = 1.5, colour = "yellow") +
geom_point(colour = "green", size = 4) +
scale_x_continuous("", breaks = xlabels) +
theme(axis.text.x = element_text(angle = 45, vjust = 0.5)) +
labs(x = "", y = "fish test", title = paste0("Population growth"))
}
}
})
output$plot <- renderPlot({
create_plot()
})
output$downloadPlot <- downloadHandler(
filename = function() "plot.png",
content = function(file) {
ggsave(create_plot(), filename = file)
}
)
}
shinyApp(ui = ui, server = server)