如何在R ggplot中为dotplot选择正确的参数

Question

I intend to make a dot plot somewhat like this:

But there's some issue with the code:

df = data.frame(x=runif(100))

df %>%
  ggplot(aes(x )) + 
  geom_dotplot(binwidth =0.01, aes(fill = ..count..), stackdir = "centerwhole",dotsize=2, stackgroups = T, binpositions = "all") 

how to choose bin width to avoid dots overlapping, bins wrapping itself in 2 columns or dots get truncated at the top and bottom?

And why is the y axis showing decimal points instead of count? And how to color the dots by x value? I tried fill = x and no color is shown.

Answer 1

First from the help of ?geom_dotplot

When binning along the x axis and stacking along the y axis, the numbers on y axis are not meaningful, due to technical limitations of ggplot2. You can hide the y axis, as in one of the examples, or manually scale it to match the number of dots.

Thus you can try following. Note, the coloring is not completly fitting the x axis.

library(tidyverse)
df %>%
  ggplot(aes(x)) + 
  geom_dotplot(stackdir = "down",dotsize=0.8,
               fill = colorRampPalette(c("blue", "white", "red"))(100)) +
  scale_y_continuous(labels = c(0,10), breaks = c(0,-0.4)) +
  scale_x_continuous(position = "top") +
  theme_classic()

For the correct coloring, you have to calculate the bins by yourself using eg .bincode :

df %>% 
  mutate(gr=with(.,.bincode(x ,breaks = seq(0,1,1/30)))) %>% 
  mutate(gr2=factor(gr,levels = 1:30, labels = colorRampPalette(c("blue", "white", "red"))(30))) %>% 
  arrange(x) %>% 
  {ggplot(data=.,aes(x)) + 
      geom_dotplot(stackdir = "down",dotsize=0.8,
                   fill = .$gr2) +
      scale_y_continuous(labels = c(0,10), breaks = c(0,-0.4)) +
      scale_x_continuous(position = "top") +
      theme_classic()}

Answer 2

The overlap is caused by the dotsize > 1; as @Jimbuo said, the decimal values on the y axis is due to the internals of this geom; for the fill and color you can use the ..x.. computed variable:

Computed variables

x center of each bin, if binaxis is "x"

df = data.frame(x=runif(1000))
library(dplyr)
library(ggplot2)

df %>%
        ggplot(aes(x, fill = ..x.., color = ..x..)) + 
        geom_dotplot(method = 'histodot',
                     binwidth = 0.01, 
                     stackdir = "down",
                     stackgroups = T, 
                     binpositions = "all") +
        scale_fill_gradientn('', colours = c('#5185FB', '#9BCFFD', '#DFDFDF', '#FF0000'), labels = c(0, 1), breaks = c(0,1), guide = guide_legend('')) +
        scale_color_gradientn(colours = c('#5185FB', '#9BCFFD', '#DFDFDF', '#FF0000'), labels = c(0, 1), breaks = c(0,1), guide = guide_legend('')) +
        scale_y_continuous() +
        scale_x_continuous('', position = 'top') +
        # coord_equal(ratio = .25) +
        theme_classic() +
        theme(axis.line = element_blank(),
              axis.text.y = element_blank(),
              axis.ticks = element_blank(),
              aspect.ratio = .25,
              legend.position = 'bottom',
              legend.direction = 'vertical'
              )

Created on 2018-05-18 by the reprex package (v0.2.0).