How to control plot height/size in interactive RMarkdown (with Shiny)

Question

I am using Shiny together with RMarkdown to produce an interactive document, as described here.

Using the following code, I managed to plot an interactive map

```{r, echo=FALSE, warning=FALSE, message=FALSE}

g2g14 <- readOGR("input//geodata", "g2g14") # no projection needs to be specified
old_geodata <- g2g14@data

inputPanel(
  selectInput("map.party", label = "Partei", choices = unique(long_data$Partei), selected = "FDP"),
  selectInput("map.year", label = "Wahljahr", choices = unique(format.Date(long_data$Jahr, "%Y")), selected = "1971")
)

renderPlot({
  partydata <- long_data %>%
    filter(Partei == input$map.party & Jahr == as.Date(input$map.year, "%Y"))
  g2g14@data <- old_geodata
  g2g14@data <- merge(g2g14@data, partydata, by.x =  "GMDNR",by.y ="BFSNr")

  cols <- brewer.pal(5, "Purples")
  brks <- seq(0,100,20)
  colsForMap <- cols[findInterval(g2g14@data$Staerke, vec = brks[1:5])]

  plot(g2g14, col = colsForMap, border = "white")
  legend("topleft", legend = levels(cut(g2g14@data$Staerke, brks)), fill = cols, border = "white", title = "Parteistärke in %")

})

The problem: The map is nicely scaled when running the code from the console, but in the interactive document, the plot is too small:

This probably results from the limited height of the plotting region. I've already tried setting a really large fig.height = 20 in the chunk options, but with no outcome. What to do?

Answer 1

You can do this with a single extra step -- add a renderUI:

```{r, echo=FALSE, warning=FALSE, message=FALSE}

g2g14 <- readOGR("input//geodata", "g2g14") # no projection needs to be specified
old_geodata <- g2g14@data

inputPanel(
  selectInput("map.party", label = "Partei", choices = unique(long_data$Partei), selected = "FDP"),
  selectInput("map.year", label = "Wahljahr", choices = unique(format.Date(long_data$Jahr, "%Y")), selected = "1971")
)

output$unsized <- renderPlot({
  partydata <- long_data %>%
    filter(Partei == input$map.party & Jahr == as.Date(input$map.year, "%Y"))
  g2g14@data <- old_geodata
  g2g14@data <- merge(g2g14@data, partydata, by.x =  "GMDNR",by.y ="BFSNr")

  cols <- brewer.pal(5, "Purples")
  brks <- seq(0,100,20)
  colsForMap <- cols[findInterval(g2g14@data$Staerke, vec = brks[1:5])]

  plot(g2g14, col = colsForMap, border = "white")
  legend("topleft", legend = levels(cut(g2g14@data$Staerke, brks)), fill = cols, border = "white", title = "Parteistärke in %")

})

renderUI({
  plotOutput("unsized", height = 500, width = 500)
})
```

Tested with the example document that is created when you start a new RMD-shiny doc:

```{r, echo=FALSE}
inputPanel(
  selectInput("n_breaks", label = "Number of bins:",
              choices = c(10, 20, 35, 50), selected = 20),

  sliderInput("bw_adjust", label = "Bandwidth adjustment:",
              min = 0.2, max = 2, value = 1, step = 0.2)
)

output$unsized <- renderPlot({
  hist(faithful$eruptions, probability = TRUE, breaks = as.numeric(input$n_breaks),
       xlab = "Duration (minutes)", main = "Geyser eruption duration")

  dens <- density(faithful$eruptions, adjust = input$bw_adjust)
  lines(dens, col = "blue")
})

renderUI({
  plotOutput("unsized", height = 250, width = 250)
})

```