I am trying to produce a heat map using ggplot2. I found this example, which I am essentially trying to replicate with my data, but I am having difficulty. My data is a simple .csv file that looks like this:
people,apple,orange,peach
mike,1,0,6
sue,0,0,1
bill,3,3,1
ted,1,1,0
I would like to produce a simple heat map where the name of the fruit is on the x-axis and the person is on the y-axis. The graph should depict squares where the color of each square is a representation of the number of fruit consumed. The square corresponding to mike:peach
should be the darkest.
Here is the code I am using to try to produce the heatmap:
data <- read.csv("/Users/bunsen/Desktop/fruit.txt", head=TRUE, sep=",")
fruit <- c(apple,orange,peach)
people <- data[,1]
(p <- ggplot(data, aes(fruit, people)) + geom_tile(aes(fill = rescale), colour = "white") + scale_fill_gradient(low = "white", high = "steelblue"))
When I plot this data I get the number of fruit on the x-axis and people on the y-axis. I also do not get color gradients representing number of fruit. How can I get the names of the fruits on the x-axis with the number of fruit eaten by a person displayed as a heat map? The current output I am getting in R looks like this:
To be honest @dr.bunsen - your example above was poorly reproducable and you didn't read the first part of the tutorial that you linked. Here is probably what you are looking for:
library(reshape)
library(ggplot2)
library(scales)
data <- structure(list(people = structure(c(2L, 3L, 1L, 4L),
.Label = c("bill", "mike", "sue", "ted"),
class = "factor"),
apple = c(1L, 0L, 3L, 1L),
orange = c(0L, 0L, 3L, 1L),
peach = c(6L, 1L, 1L, 0L)),
.Names = c("people", "apple", "orange", "peach"),
class = "data.frame",
row.names = c(NA, -4L))
data.m <- melt(data)
data.m <- ddply(data.m, .(variable), transform, rescale = rescale(value))
p <- ggplot(data.m, aes(variable, people)) +
geom_tile(aes(fill = rescale), colour = "white")
p + scale_fill_gradient(low = "white", high = "steelblue")
Seven (!) years later, the best way to format your data correctly is to use tidyr
rather than reshape
Using gather
from tidyr
, it is very easy to reformat your data to get the expected 3 columns (person
for the y-axis, fruit
for the x-axis and count
for the values):
library("dplyr")
library("tidyr")
hm <- readr::read_csv("people,apple,orange,peach
mike,1,0,6
sue,0,0,1
bill,3,3,1
ted,1,1,0")
hm <- hm %>%
gather(fruit, count, apple:peach)
#syntax: key column (to create), value column (to create), columns to gather (will become (key, value) pairs)
The data now looks like:
# A tibble: 12 x 3
people fruit count
<chr> <chr> <dbl>
1 mike apple 1
2 sue apple 0
3 bill apple 3
4 ted apple 1
5 mike orange 0
6 sue orange 0
7 bill orange 3
8 ted orange 1
9 mike peach 6
10 sue peach 1
11 bill peach 1
12 ted peach 0
Perfect! Let's get plotting. The basic geom to do a heatmap with ggplot2 is geom_tile
to which we'll provide aesthetic x
, y
and fill
.
library("ggplot2")
ggplot(hm, aes(x=x, y=y, fill=value)) + geom_tile()
OK not too bad but we can do much better.
theme_bw()
which gets rid of the grey background. I also like to use a palette from RColorBrewer
(with direction = 1
to get the darker colors for higher values, or -1 otherwise). There is a lot of available palettes: Reds, Blues, Spectral, RdYlBu (red-yellow-blue), RdBu (red-blue), etc. Below I use "Greens". Run RColorBrewer::display.brewer.all()
to see what the palettes look like.
If you want the tiles to be squared, simply use coord_equal()
.
I often find the legend is not useful but it depends on your particular use case. You can hide the fill
legend with guides(fill=F)
.
You can print the values on top of the tiles using geom_text
(or geom_label
). It takes aesthetics x
, y
and label
but in our case, x
and y
are inherited. You can also print higher values bigger by passing size=count
as an aesthetic -- in that case you will also want to pass size=F
to guides
to hide the size legend.
You can draw lines around the tiles by passing a color
to geom_tile
.
Putting it all together:
ggplot(hm, aes(x=fruit, y=people, fill=count)) +
# tile with black contour
geom_tile(color="black") +
# B&W theme, no grey background
theme_bw() +
# square tiles
coord_equal() +
# Green color theme for `fill`
scale_fill_distiller(palette="Greens", direction=1) +
# printing values in black
geom_text(aes(label=count), color="black") +
# removing legend for `fill` since we're already printing values
guides(fill=F) +
# since there is no legend, adding a title
labs(title = "Count of fruits per person")
To remove anything, simply remove the corresponding line.
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