Contour Plots in ggplot2

Basic geom_contour plot

geom_contour produces a similar output to geom_density_2d, except it uses a third variable for the values rather than frequency. The volcano dataset comes pre-loaded on R.

library(plotly)
library(reshape2)
df <- melt(volcano)

p <- ggplot(df, aes(Var1, Var2, z= value)) +
  geom_contour() +
  scale_fill_distiller(palette = "Spectral", direction = -1)

ggplotly(p)

Coloured Plot

See here for a list of colour palettes that come with the brewer (discrete) and distiller (continuous) packages.

library(plotly)
library(reshape2)
df <- melt(volcano)

p <- ggplot(df, aes(Var1, Var2, z= value, colour=stat(level))) +
  geom_contour() +
  scale_colour_distiller(palette = "YlGn", direction = 1)

ggplotly(p)

Filled Plot

It's possible to colour in each of the layers, by changing geom_contour to stat_contour as below. As the edges of the graph indicate, filled contour plots only work when each layer is an enclosed shape rather than an open line; a geom more suited to this functionality would be geom_tile or geom_raster.

library(plotly)
library(reshape2)
df <- melt(volcano)

p <- ggplot(df, aes(Var1, Var2, z= value)) +
  stat_contour(geom="polygon",aes(fill=stat(level))) +
  scale_fill_distiller(palette = "Spectral", direction = -1)

ggplotly(p)

What About Dash?

Dash for R is an open-source framework for building analytical applications, with no Javascript required, and it is tightly integrated with the Plotly graphing library.

Learn about how to install Dash for R at https://dashr.plot.ly/installation.

Everywhere in this page that you see fig, you can display the same figure in a Dash for R application by passing it to the figure argument of the Graph component from the built-in dashCoreComponents package like this:

library(plotly)

fig <- plot_ly() 
# fig <- fig %>% add_trace( ... )
# fig <- fig %>% layout( ... ) 

library(dash)
library(dashCoreComponents)
library(dashHtmlComponents)

app <- Dash$new()
app$layout(
    htmlDiv(
        list(
            dccGraph(figure=fig) 
        )
     )
)

app$run_server(debug=TRUE, dev_tools_hot_reload=FALSE)