Slope Chart - ggplot2 - r

Question

I am testing some templates of ggplot2, and I am interesting to the slope chart, available from here:
Slope Chart - Link
It works perfectly.
I am only trying to make a similar one but with only a group defined, like the following code:
library(dplyr)
library(ggplot2)
theme_set(theme_classic())
source_df <- read.csv("https://raw.githubusercontent.com/jkeirstead/r-slopegraph/master/cancer_survival_rates.csv")
source_df <- filter(source_df, group == "Thyroid")
then I copy the remaining code from the example:
# Define functions. Source: https://github.com/jkeirstead/r-slopegraph
tufte_sort <- function(df, x="year", y="value", group="group", method="tufte", min.space=0.05) {
## First rename the columns for consistency
ids <- match(c(x, y, group), names(df))
df <- df[,ids]
names(df) <- c("x", "y", "group")
## Expand grid to ensure every combination has a defined value
tmp <- expand.grid(x=unique(df$x), group=unique(df$group))
tmp <- merge(df, tmp, all.y=TRUE)
df <- mutate(tmp, y=ifelse(is.na(y), 0, y))
## Cast into a matrix shape and arrange by first column
require(reshape2)
tmp <- dcast(df, group ~ x, value.var="y")
ord <- order(tmp[,2])
tmp <- tmp[ord,]
min.space <- min.space*diff(range(tmp[,-1]))
yshift <- numeric(nrow(tmp))
## Start at "bottom" row
## Repeat for rest of the rows until you hit the top
for (i in 2:nrow(tmp)) {
## Shift subsequent row up by equal space so gap between
## two entries is >= minimum
mat <- as.matrix(tmp[(i-1):i, -1])
d.min <- min(diff(mat))
yshift[i] <- ifelse(d.min < min.space, min.space - d.min, 0)
}
tmp <- cbind(tmp, yshift=cumsum(yshift))
scale <- 1
tmp <- melt(tmp, id=c("group", "yshift"), variable.name="x", value.name="y")
## Store these gaps in a separate variable so that they can be scaled ypos = a*yshift + y
tmp <- transform(tmp, ypos=y + scale*yshift)
return(tmp)
}
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)
}
## Prepare data
df <- tufte_sort(source_df,
x="year",
y="value",
group="group",
method="tufte",
min.space=0.05)
df <- transform(df,
x=factor(x, levels=c(5,10,15,20),
labels=c("5 years","10 years","15 years","20 years")),
y=round(y))
## Plot
plot_slopegraph(df) + labs(title="Estimates of % survival rates") +
theme(axis.title=element_blank(),
axis.ticks = element_blank(),
plot.title = element_text(hjust=0.5,
family = "American Typewriter",
face="bold"),
axis.text = element_text(family = "American Typewriter",
face="bold"))
The problem I find is that the connecting lines disappears if I take only one object in source_df$group ()in this case Thyroid, like the followings:
If I add only another item in the same column everything is fine and the connecting line appears.
Is there a way to have the lines also in this situation? I have tried on a lot of ways, removing the lines containing NA values without success, therefore I do not know how to fix this problem, if ... it is possible to be fixed.
Thank you in advance for every eventual reply!

Answer 1

May I suggest a much easier way, with the {ggh4x} package, which has a base R type = "b" like geom. You can remove the points, and plot text instead.
You'll get your result in three lines of code :)
library(tidyverse)
library(ggh4x)
source_df <- read.csv("https://raw.githubusercontent.com/jkeirstead/r-slopegraph/master/cancer_survival_rates.csv")
source_df <- filter(source_df, group == "Thyroid")
ggplot(source_df, aes(year, value)) +
## set shape to NA
geom_pointpath(aes(group = group, mult = 1), shape = NA) +
geom_text(aes(label = value))
Created on 2021-12-30 by the reprex package (v2.0.1)

Answer 2

I fixed simply adding the line:
df <- df[complete.cases(df), ]
Before the graphing instructions. The problem was the generation of many lines with NA values and this line removes lines with null value.