Trouble with horizontal and vertical lines accepting class "Date" in ggplot?

Question

I'm trying to make a Gantt chart in ggplot based on the generous code offered by user Didzis Elferts. I'm trying to add a vertical line showing today's date, but the `geom_vline` layer in the `ggplot2` package simply returns `Error: Discrete value supplied to continuous scale`. Here is my code: ``` today <- as.Date(Sys.Date(), "%m/%d/%Y") library(scales) ggplot(mdfr, aes(time,name, colour = is.critical)) + geom_line(size = 6) + xlab("") + ylab("")+ labs(title="Sample Project Progress")+ theme_bw()+ scale_x_datetime(breaks=date_breaks("1 year"))+ geom_vline(aes(xintercept=today)) ``` The plot without the `geom_vline` command looks like this : Any reason why `geom_vline` wouldn't work for the "Date" character? EDIT: Reproducible code used to generate plot: ``` ### GANTT CHART 1 ###############3 tasks <- c("Meetings", "Client Calls", "Design", "Bidding", "Construction") dfr <- data.frame( name = factor(tasks, levels = tasks), start.date = c("07/08/2013", "07/08/2013", "07/23/2013", "08/3…

Accepted Answer

There are two thinks you need to change in your code.

First, as for making the `time` column in `mdfr` you use `as.POSIXct()` the same should be done with `today` - both variables should have the same format.

```
today <- as.POSIXct(Sys.Date(), "%m/%d/%Y")
```

Second, use `as.numeric()` inside the `geom_vline()` around `today`.

```
  + geom_vline(aes(xintercept=as.numeric(today)))
```

Trouble with horizontal and vertical lines accepting class "Date" in ggplot?

Solution

Problem