Decimal digits in `Slope Graph` with `ggplot2` - r

Question

Following a former question I opened few weeks ago:
Slope Chart - ggplot2
I face another issue, concerning the numeric values reported in the graph. Even specifying the decimal digits I need (exactly 3) with any of the two commands:
y=round(y, digit = 3) at the endof the code
or
options(digits=3) at the beginning of the whole code
The graphical output, doesn't give me the desired number of digits but only concerning 0. In the graph, I wanted to have 0.800 (not 0.8) and 0.940 (not 0.94). It looks like it removes 0. Below the graphical output from R, I circled in red the number I intended to change.
Below the whole code:
library(dplyr)
library(ggplot2)
#options(digits=3)
theme_set(theme_classic())
#### Data
df <- structure(list(group = c("Ups", "Ups", "Ups", "Ups", "Ups"),
yshift = c(0, 0, 0, 0, 0), x = structure(1:5, .Label = c("1 day",
"2 days", "3 days", "5 days", "7 days"), class = "factor"),
y = c(0.108, 0.8, 0.94, 1.511, 1.905), ypos = c(0.10754145,
0.8, 0.94, 1.5111111, 1.90544651164516)), row.names = c(1L,
3L, 5L, 7L, 9L), class = "data.frame")
# Define functions. Source: https://github.com/jkeirstead/r-slopegraph
plot_slopegraph <- function(df) {
ylabs <- subset(df, x==head(x,1))$group
yvals <- subset(df, x==head(x,1))$ypos
fontSize <- 3
gg <- ggplot(df,aes(x=x,y=ypos)) +
geom_line(aes(group=group),colour="grey80") +
geom_point(colour="white",size=8) +
geom_text(aes(label=y), size=fontSize, family="American Typewriter") +
scale_y_continuous(name="", breaks=yvals, labels=ylabs)
return(gg)
}
## Plot
plot_slopegraph(df) + labs(title="Monomer content after days of heating")
I am making any mistake or missing something? Is there any other way to force 0 digits?
Thank you in advance for every eventual reply or comment.

Answer 1

I like the scales package functions for things like this (though you could certainly use formatC or sprintf instead).
I've modified plot_slopegraph to use label=scales::label_number(accuracy = 0.001)(y)) in the geom_text():
plot_slopegraph <- function(df) {
ylabs <- subset(df, x==head(x,1))$group
yvals <- subset(df, x==head(x,1))$ypos
fontSize <- 3
gg <- ggplot(df,aes(x=x,y=ypos)) +
geom_line(aes(group=group),colour="grey80") +
geom_point(colour="white",size=8) +
geom_text(aes(label=scales::label_number(accuracy = 0.001)(y)), size=fontSize, family="American Typewriter") +
scale_y_continuous(name="", breaks=yvals, labels=ylabs)
return(gg)
}
plot_slopegraph(df)