dotplot with ggplot2 grouping the y values

Question

I have a data-set similar to this

products <- c('Product1', 'Product2', 'Product3', 'Product3', 'Product1', 'Product1')
timestamp <- c(1,2,3,4,5,6)
categories <- c('Category1', 'Category2', 'Category1', 'Category1', 'Category1', 'Category1')
data <- data.frame(timestamp, products, categories)

Now I would like to draw a dotplot with ggplot2 like so

ggplot(data, aes(timestamp, products, colour=categories, group=categories)) + geom_point()

Which produces the following chart

enter image description here

Which is almost what I what, however, I would like to group the products in categories as they are in this chart:

dotchart(data$timestamp, labels=data$products, groups=data$categories, color=data$color)

enter image description here

It is important to plot occurrences of a product for the same y-value (like in the first plot), instead of repeating it for every record as it is done in the second plot.

is + facet_wrap(~categories) useful to you

tospig
– tospig

2015-07-09 05:40:22 +00:00
Commented Jul 9, 2015 at 5:40 — tospig
– tospig, Commented Jul 9, 2015 at 5:40

mathematical.coffee · Accepted Answer · 2015-07-09 05:43:06Z

5

You could try just making a new y column like so:

type <- paste(data$categories, data$products)
# convert to a factor and sort the levels reverse-alphabetical (so it is in order top-down on the plot)
type <- factor(type, levels=sort(unique(type), dec=T))
data$type <- type
ggplot(data, aes(timestamp, type, colour=categories)) + geom_point()

enter image description here

though the y axis text is not laid out like in the dotchart.

Or you could use facet_wrap for something similar but a bit different (don't need the type thing then):

ggplot(data, aes(timestamp, products, colour=categories)) + geom_point() + facet_wrap( ~ categories,ncol=1)

enter image description here

This one provides more separation of your categories and has the advantage (or perhaps disadvantage, depending on your opinion) of showing "empty" level combinations (e.g. category 2 product 1). If you don't like that add scales="free_y":

ggplot(data, aes(timestamp, products, colour=categories)) + geom_point() + facet_wrap( ~ categories, ncol=1, scales="free_y")

enter image description here

answered Jul 9, 2015 at 5:43

mathematical.coffee

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4 Comments

brancz Over a year ago

Is there a way to plot it in one chart? I have a rather huge dataset.

mathematical.coffee Over a year ago

The first option is in one chart.

mathematical.coffee Over a year ago

If all you want to do is remove the vertical whitespace on the last option, do a + theme(panel.margin=unit(0, 'lines')) (you also need library(grid) to get to unit). As for vertical spacing between the y axis lines (between Product 3 and Product 1 for example), if you squish your plot window vertically these will also squish together.

brancz Over a year ago

sorry about that, the first chart is exactly what I was looking for :) little overwhelmed by the extend of your skill :D

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