How to choose the right parameters for dotplot in r ggplot - r

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

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).

Answer 2

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 e.g. .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()}