How to plot data in a chronological order while showing numerical labels on the x axis in ggplot 2

I have a data frame like this:

df <- data.frame( Time = as.POSIXct(c("2023-08-01 08:00:00", "2023-08-01 12:00:00","2023-08-05 08:00:00", "2023-08-05 12:00:00","2023-08-10 08:00:00", "2023-08-10 12:00:00","2023-08-15 08:00:00", "2023-08-15 12:00:00")),  DAS = c(0, 0, 4, 4, 9, 9, 14, 14), emmean = c(10, 15, 20, 25, 30, 35, 40, 45) )

I am trying to plot my data in a chronological order (so I need the posixct format I think) while using the numerical DAS values on my x-axis.

p<-ggplot(df, aes(x = Time, y = emmean)) + geom_point()

Basically the two options that get the closest results are:

1. p + scale_x_continuous(breaks = df$Time, labels = df$DAS)
2. p + scale_x_datetime(breaks = df$Time, labels = df$DAS, date_breaks = "1 day", date_labels = "%b %d")

The problem with 1 is that I get the DAS label repeated for each timepoint, which is an issue with my data, as there are way too many points. I want one DAS value for the whole day, not per measurement.
The problem with 2 is that is still shows the date instead of the DAS values.
I would like the break frequency of option 2 with the labeling of option 1.

Is there a way to do this?

>Solution :

It looks as though DAS is the number of days since the first measurement. One option would be to have this explicitly calculated on-the-fly. Simply subtract min(Time) from Time, which will give you the number of seconds since the first measurement. Convert this to days by dividing by 86400 (the number of seconds in a day)

ggplot(df, aes(x = as.numeric(Time - min(Time))/86400, y = emmean)) + 
 geom_point() +
 xlab('DAS')