# geomtextpath
**Repository Path**: tidyfriday/geomtextpath
## Basic Information
- **Project Name**: geomtextpath
- **Description**: No description available
- **Primary Language**: Unknown
- **License**: MIT
- **Default Branch**: main
- **Homepage**: None
- **GVP Project**: No
## Statistics
- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-11-30
- **Last Updated**: 2021-11-30
## Categories & Tags
**Categories**: Uncategorized
**Tags**: None
## README
# geomtextpath 
[](https://CRAN.R-project.org/package=geomtextpath)
[](https://github.com/AllanCameron/geomtextpath/actions)
[](https://codecov.io/gh/AllanCameron/geomtextpath?branch=main)
## Create curved text in ggplot2
The existing text-based geom layers in ggplot2 (`geom_text` and
`geom_label`) are ideal for the majority of plots, since typically
textual annotations are short, straight and in line with the axes of the
plot. However, there are some occasions when it is useful to have text
follow a curved path. This may be to create or recreate a specific
visual effect, or it may be to label a circular / polar plot in a more
“natural” way.
## Installation
You can install the development version of geomtextpath from
[GitHub](https://github.com/) with:
``` r
# install.packages("remotes")
remotes::install_github("AllanCameron/geomtextpath")
```
## Examples
``` r
library(geomtextpath)
#> Loading required package: ggplot2
```
### Plotting text along an arbitrary path
``` r
t <- seq(-1, 5, length.out = 1000) * pi
spiral <- data.frame(
x = rev(sin(t) * 1000:1),
y = rev(cos(t) * 1000:1),
s = seq(1, 10, length.out = 100),
text = paste(
"Like a circle in a spiral, like a wheel within a wheel,",
"never ending or beginning on an ever spinning reel"
)
)
ggplot(spiral, aes(x, y, label = text)) +
geom_textpath(size = 7, vjust = 2, linewidth = 0) +
coord_equal(xlim = c(-1500, 1500), ylim = c(-1500, 1500))
```
### Produce labelled density lines
By default, the paths are broken to allow the names in-line.
``` r
ggplot(iris, aes(x = Sepal.Length, colour = Species)) +
geom_textpath(aes(label = Species), stat = "density",
size = 6, fontface = 2, hjust = 0.2, vjust = 0.3)
```
If the `vjust` parameter moves the text above or below the line, the
line is automatically filled in.
``` r
ggplot(iris, aes(x = Sepal.Length, colour = Species)) +
geom_textpath(aes(label = Species), stat = "density",
size = 6, fontface = 2, hjust = 0.2, vjust = -0.2)
```
### Correction of angles across different aspect ratios
The angle of the text continues to follow the path even if the aspect
ratio of the plot changes, for example, during faceting. Compare
faceting horizontally:
``` r
p <- ggplot(iris, aes(x = Sepal.Length, colour = Species)) +
geom_textpath(aes(label = Species), stat = "density",
size = 6, fontface = 2, hjust = 0.2, vjust = -0.2) +
scale_y_continuous(limits = c(0, 1.5))
p + facet_grid(.~Species)
```
to faceting vertically:
``` r
p + facet_grid(Species~.)
```
The text will continue to rotate appropriately as the plotting window is
rescaled.
### Labelling groups of point along their trend line
``` r
ggplot(iris, aes(x = Sepal.Length, y = Petal.Length)) +
geom_point(alpha = 0.1) +
geom_textpath(aes(label = Species, colour = Species),
stat = "smooth", method = "loess", formula = y ~ x,
size = 7, linetype = 3, fontface = 2, linewidth = 1) +
scale_colour_manual(values = c("forestgreen", "deepskyblue4", "tomato4")) +
theme_bw()
```
### Text paths in polar coordinates
Straight text paths in Cartesian coordinates become curved in polar
coordinates.
``` r
df <- data.frame(x = c(1, 1000), y = 1, text = "This is a perfectly flat label")
p <- ggplot(df, aes(x, y, label = text)) +
geom_textpath(size = 6) +
ylim(c(0.9, 1.1))
p
```
``` r
p + coord_polar(start = pi)
```
We can even construct complex diagrammatic plots:
``` r
p <- data.frame(x1 = c(seq(0, 10/6 * pi, pi/3),
seq(0, 10/6 * pi, 2*pi/3)),
y1 = c(rep(2, 6), rep(-1, 3)),
x2 = c(seq(0, 10/6 * pi, pi/3) + pi/3,
seq(0, 10/6 * pi, 2*pi/3) + 2*pi/3),
y2 = c(rep(4, 6), rep(2, 3)),
group = letters[c(1:6, (1:3) * 2)],
alpha = c(rep(1, 6), rep(0.4, 3))) |>
ggplot(aes(x1, y1)) +
geom_rect(aes(xmin = x1, xmax = x2, ymin = y1, ymax = y2, fill = group,
alpha = alpha),
color = "white", size = 2) +
geom_textpath(data = data.frame(x1 = seq(0, 2 * pi, length = 300),
y1 = rep(0.5, 300),
label = rep(c("stats", "effects", "polar"), each = 100)),
aes(label = label), linetype = 0, size = 8,
flip_inverted = TRUE) +
geom_textpath(data = data.frame(x1 = seq(0, 2 * pi, length = 300),
y1 = rep(3, 300),
label = rep(c("density", "smooth", "unique", "organic",
"easy to use", "automatic"),
each = 50)),
aes(label = label), linetype = 0, size = 4.6, color = "white",
flip_inverted = TRUE) +
scale_y_continuous(limits = c(-5, 4)) +
scale_x_continuous(limits = c(0, 2*pi)) +
scale_fill_manual(values = c("deepskyblue3", "deepskyblue4",
"green3", "green4","tomato", "tomato2")) +
scale_alpha_identity() +
theme_void() +
theme(legend.position = "none")
p
```
That flip nicely to polar co-ordinates.
``` r
p + coord_polar()
```
## Limitations
There are limitations inherent in the plotting of text elements in
ggplot due to the way that the underlying `grid` graphics handles text.
A text string is dealt with as a zero-width object, and therefore the
rotation and spacing of the letters making up the string can only be
dealt with by treating each letter separately.
It is important to realise that the letters are only rotated, and do not
undergo any change in shape. Thus, for example, large text appearing on
convex curves will not be deformed so that individual letters are
narrower at the bottom and wider at the top. Doing so would require
reinterpreting the letters as polygons.
Another issue is that we may wish to use a short curved label on a much
longer path. Spacing the letters equally along the path would mean there
is too much space between the letters for the label to remain legible. A
single text string is therefore kept “together” according to the point
size of the text in `geom_textpath`. This then leaves the problem of
where on the path the text should be placed. This can be dealt with by
the aesthetic mapping `hjust`, which allows the user to place the labels
at the desired position along the path, including separate positions for
each label.
A final point to note is that a path is usually a group-based geom
(i.e. a path typically comprises x, y points from two columns over
several rows of a data frame), whereas text labels can come from single
rows in a data frame. This means that if we have a data frame with an x
column, a y column and a grouping variable column, there can only be a
single label for the group. Typically, this will be the grouping
variable itself (see the examples, particularly those using the built-in
iris data set.)