Making curved text on coord_polar - r

Question

I want make curved text around ggplot with coord_polar. I have data.frame:
z <- data.frame( a=c("sensor 1","sensor 2","sensor 3","sensor 4","sensor 5","sensor 6","sensor 7","sensor 8"), b=c(50, 60, 70, 20,90,110,30,100))
And here is code where I create my ggplot:
cxc <- ggplot(z, aes(x=a, y=b, fill=factor(b))) +
geom_bar(width = 1,stat="identity",colour = "black")
cxc + coord_polar() +
theme_linedraw() +theme(axis.ticks =element_blank(), axis.text.y =element_blank(), axis.title=element_blank(), axis.text.x=element_text(size = 12,angle = 45))
Here is image from my result. I want making texts (x axis): sensor 1, sensor 2... making curved like I draw with red color around circle from coord_polar. Must fit with circle.

Answer 1

I am not sure on curving the text, but if you want them to at least rotate, this is a start:
myAng <-
seq(-20,-340,length.out = 8)
cxc + coord_polar() +
theme_linedraw() +
theme(axis.ticks =element_blank()
, axis.text.y =element_blank()
, axis.title=element_blank()
, axis.text.x=element_text(size = 12
,angle = myAng))
I will add in my hesitation on using such angles (or even polar coordinates for a plot like this). However, I assume that you have a good reason for doing it, and that this MWE just doesn't show it.

Answer 2

The {geomtextpath} package has a dedicated function for exactly this use case, including curved text. See also: here.
library(ggplot2)
library(geomtextpath) # remotes::install_github("AllanCameron/geomtextpath")
z <- data.frame(
a=c("sensor 1","sensor 2","sensor 3","sensor 4",
"sensor 5","sensor 6","sensor 7","sensor 8"),
b=c(50, 60, 70, 20,90,110,30,100)
)
cxc <- ggplot(z, aes(x=a, y=b, fill=factor(b))) +
geom_bar(width = 1,stat="identity",colour = "black")
cxc + coord_curvedpolar() +
theme_linedraw() +
theme(axis.ticks =element_blank(),
axis.text.y =element_blank(),
axis.title=element_blank(),
axis.text.x=element_text(size = 12))
Created on 2021-12-08 by the reprex package (v2.0.1)
Disclaimer: I'm a co-author of that package.

Answer 3

I don't know of a way to make them curve exactly like that using ggplot2 but we can at least remove the funny angle...
pm <- grid::unit(c(2, 2, 2, 2), "cm")
RadarTheme<-theme(panel.background=element_blank(),
plot.title= element_text(size = 25,face=c("bold","italic")),
plot.margin = pm,
text=element_text(family="Open Sans"), aspect.ratio = 1,
legend.position="bottom",legend.title=element_blank(),legend.direction="vertical",
strip.text.x = element_text(size = rel(0.8)),
axis.text.x = element_text(size = 15,face ="bold"),
axis.ticks.y = element_blank(),
axis.text.y = element_blank(),
axis.line.x=element_line(size=0.5),
panel.grid.major=element_line(size=0.3,linetype = 2,colour="grey"))
cxc <- ggplot(z, aes(x=a, y=b, fill=factor(b))) +
geom_bar(width = 1,stat="identity",colour = "black")
cxc + coord_polar() + RadarTheme