Continuous Color Scales and Color Bars in ggplot2

How to make Continuous Color Scales and Color Bars in ggplot2 with Plotly.

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Default colour scale

library(plotly)
library(ggplot2)

df <- data.frame(
  x = runif(100),
  y = runif(100),
  z1 = rnorm(100),
  z2 = abs(rnorm(100))
)

p <- ggplot(df, aes(x, y)) +
      geom_point(aes(colour = z2))

ggplotly(p)

Diverging colour scales

library(plotly)
library(ggplot2)

df <- data.frame(
  x = runif(100),
  y = runif(100),
  z1 = rnorm(100),
  z2 = abs(rnorm(100))
)

p <- ggplot(df, aes(x, y)) +
      geom_point(aes(colour = z1)) +
      scale_colour_gradient2()

ggplotly(p)

Custom colour gradient

library(plotly)
library(ggplot2)

df <- data.frame(
  x = runif(100),
  y = runif(100),
  z1 = rnorm(100),
  z2 = abs(rnorm(100))
)

p <- ggplot(df, aes(x, y)) +
      geom_point(aes(colour = z1)) +
      scale_colour_gradientn(colours = terrain.colors(10))

ggplotly(p)

You can achievethe same result with the following aesthetic setup:

library(plotly)
library(ggplot2)

p <- ggplot(faithfuld, aes(waiting, eruptions)) +
      geom_raster(aes(fill = density)) +
      scale_fill_gradientn(colours = terrain.colors(10))

ggplotly(p)

Adjust colour choices with low and high

library(plotly)
library(ggplot2)

df <- data.frame(
  x = runif(100),
  y = runif(100),
  z1 = rnorm(100),
  z2 = abs(rnorm(100))
)

p <- ggplot(df, aes(x, y)) +
  geom_point(aes(colour = z2)) +
  scale_colour_gradient(low = "white", high = "black")

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)