Making a Stacked Bar Chart Out of Table Columns in R - r

Question

I'm trying to create a stacked bar graph showing body composition. I have a table/data set (I don't know the correct term) that looks like this:
structure(list(data.Date = structure(1:7, .Label = c("2021-03-06",
"2021-03-07", "2021-03-08", "2021-03-09", "2021-03-10", "2021-03-11",
"2021-03-12"), class = "factor"), total_bf = c(19.6612, 18.2182,
19.6803, 21.7047, 18.126, 19.7, 19.1424), total_muscle = c(41.5948,
43.043, 42.1578, 42.1866, 43.4017, 42.2, 42.2728), other = c(37.544,
38.8388, 38.0619, 38.0087, 39.1723, 38.1, 38.2848)), class = "data.frame", row.names = c(NA,
-7L))
Each column is a weight in kilograms. Together they add up to the total body weight of the subject. What I want is a stacked bar graph where each bar represents a date and each bar is split by total_bf, total_muscle and other. All of the guides and Q&As I've seen don't seem to apply to my situation. Maybe this is because I am new but nothing I've tried has worked yet.
An example of what I'm trying to achieve:
The only difference is that on my graph blue would be body fat (total_bf), green would be other and red would be muscle (total_muscle).

Answer 1

You can convert data from the wide format to the long format using tidyr::pivot_longer() function:
library(ggplot2)
df <- structure(list(
data.Date = structure(
1:7,
.Label = c("2021-03-06", "2021-03-07", "2021-03-08", "2021-03-09",
"2021-03-10", "2021-03-11", "2021-03-12"), class = "factor"),
total_bf = c(19.6612, 18.2182, 19.6803, 21.7047, 18.126, 19.7, 19.1424),
total_muscle = c(41.5948, 43.043, 42.1578, 42.1866, 43.4017, 42.2, 42.2728),
other = c(37.544, 38.8388, 38.0619, 38.0087, 39.1723, 38.1, 38.2848)
), class = "data.frame", row.names = c(NA, -7L))
long <- tidyr::pivot_longer(df, -data.Date)
Then using ggplot2, the defaults already make a stacked bar chart, so you just need to specify x, y and fill aesthetics.
ggplot(long, aes(data.Date, value, fill = name)) +
geom_col()
Since your date is encoded as a factor, if you want to encode it as a real date you can convert it as follows:
long$date <- as.Date(strptime(as.character(long$data.Date), format = "%Y-%m-%d"))
ggplot(long, aes(date, value, fill = name)) +
geom_col()
Created on 2021-03-12 by the reprex package (v0.3.0)