R Shiny Renderimage() Does Not Recognize Object 'input'

Why does renderImage() not recognize input in the code sample below: library(d3heatmap) library(shiny) library(ggplot2) ui <- fluidPage( h1('A heatmap demo'),

Solution 1:

d3heatmap() produce the htmlwidgets class object. We can use saveWidget() function from the htmlwidgets package to save plot.

library(d3heatmap)
library(shiny)
library(htmlwidgets)

ui <- fluidPage(
    h1("A heatmap demo"),
    selectInput("palette", "Palette", c("YlOrRd", "RdYlBu", "Greens", "Blues")),
    checkboxInput("cluster", "Apply clustering"),
    downloadButton('download', 'Download Heatmap'),
    d3heatmapOutput("heatmap")
)
server <- function(input, output, session) {
    plot <- reactive({
        d3heatmap(
            scale(mtcars),
            colors = input$palette,
            dendrogram = if (input$cluster) "both" else "none"
        )
    })
    output$heatmap <- renderD3heatmap({
        plot()
    })
    output$download <- downloadHandler(
        filename = function() {
            paste0("d3heatmap-", tolower(input$palette), ".html")
        },
        content = function(file) {
            saveWidget(plot(), file)
        }
    )
}

shinyApp(ui = ui, server = server)

If you need save a plot as png see this discussion: https://github.com/ramnathv/htmlwidgets/issues/95. In short: now htmlwidgets does not support export plots as png or svg. You can see exportwidget and webshot packages as workground.