ggplot:print hourly format in x-axis

Question

I have the following data frame

df

Time Load1 Load2

0 375.5 375.5

10 374.6 374.6

20 350.1 350.1

30 334.5 334.5

40 304.9 347.7

50 285.4 331.6

.... .... .. ...

I am unable to change the format of the Time column from 10,20 to be like this: 00:10, 00:20...

I want to draw this data frame using ggplot by this command:

    P<- ggplot(df,aes(Time))+

    geom_line(aes (y=0))+

   geom_vline(xintercept = 0,)+  

    geom_line(aes(y=Load2,linetype = "twodash"))+ 

    geom_line(aes(y=Load1, linetype = "solid"))+

    theme(legend.position='none')+ # to remove the legend.

    geom_vline(xintercept = 650, colour="purple",linetype ="longdash")+

    geom_vline(xintercept = 1500, colour="purple",linetype ="longdash")+

    geom_vline(xintercept = 2200, colour="purple",linetype ="longdash")+

    labs(title = "Daily load demands", x = "Time of day", y = "Power 
consumption_Kw/h")

    P

however, the currently result is :

enter image description here

I tried following command to change the time format :

 df<- data.frame(Time,Load1,Load2)

 df$Time <- as.POSIXct(df$Time, format="%H:%M:%S")
   P<- ggplot(df,aes(df$Time))+...

But there is no change. please, is there any suggestion to draw the x-axis in the format 05:00, 10:00, 15:00, 20:00 instead of 500, 1000,1500,2000. many thanks.

Answer 1

I guess this can be your solution. If is only a problem of visualisation (and not of data) why don't you simply change the Labels in ggplot? You can use something similar to (Note: the code I am giving you here is simply an example that DON'T APPLY to your case)

scale_x_continuous( breaks = c(2012,2013,2014,2015,2016, 2017), 
      labels = c ("A","B","C","D","E","F"))

That would change labels on the x-axis from years to letters.

Answer 2

I can't tell the format of your Time entry beyond 60 minutes, but here is a possible solution. Other manipulation may be needed depending on the minute format of your data.

Convert the minutes to appropriate format, first left-pad with 0's (uses stringr package):

df$Time <- stringr::str_pad(df$Time, 4, "left", pad = "0" )

or the sprintf() from the link above is a simple, elegant solution that does the same: df$Time <- sprintf("%04d", df$Time) One might work better depending on your original Time format.

then convert this to a POSIXct format time:

df$Time <- strptime(df$Time, format = "%H%M")

Then format the time appropriately in ggplot. Using your existing plot, just add:

P + scale_x_datetime(labels = date_format("%H:%M"))