Creating a geom_line plot where as the numeric value on x-axis increased, the y-axis shows a cumulative count

I have the following data set:

df <- data.frame(
  Passwords = c("123er", "234f4", "234r4", "234f6", "234f8","274f4","294f4",
                "204f4","23yf4","2l4f4","2u4f4","23of4","734f4","834f4",
                "934f4","234w4","267f4"),
  Days_Elapsed = c(1,1,1,4,4,5,5,5,7,7,7,7,8,8,8,9,9))

The objective is to create a geom-line plot that shows an ever upwards line corresponding to the number of passwords registered as the Days-Elapsed variable increases. For example, when Days_Elapsed equals 1, there are three passwords, meaning that, in the plot, on the x-axis value for 1, there would be a y-value of 3. This value of 3 would remain consistent for Days_Elapsed 2 and 3, as no passwords were registered on these days (meaning the line would be perfectly horizontal). This line would then increase to 5 as the Days-Elapsed reach the value of 4 (because two more passwords were registered on day 4). On day 5 there are three more passwords, so the line in Y would increase to the value 8, and so on.

I reckon this is fairly simple but I just cannot find a way to get it done. Any help would be appreciated. Thank you.

>Solution :

it seems the function you were looking for is geom_step() in ggplot2. But to use it you must transform your data a bit:

1. To get the count of passwords by days elapsed
2. To get the cumulative number of days

library(dplyr)
library(ggplot2)
df <- data.frame(
  Passwords = c("123er", "234f4", "234r4", "234f6", "234f8","274f4","294f4",
                "204f4","23yf4","2l4f4","2u4f4","23of4","734f4","834f4",
                "934f4","234w4","267f4"),
  Days_Elapsed = c(1,1,1,4,4,5,5,5,7,7,7,7,8,8,8,9,9))

df |> count(Days_Elapsed) |> # for 1.
  mutate(
    n_cumul = cumsum(n) # for 2.
  ) |> 
  ggplot(aes(x = Days_Elapsed, y = n_cumul )) +
  geom_step()

Hope that helps ; )