R: Creating a ggplot2 barchart of timedate y-variable -

i'm having lot of trouble trying create otherwise simple ggplot barchart of timedate variable on y-axis. plots fine using geom_point or geom_line, replace geom_bar, r either crashes or returns me blank, grey graph.

my raw data character strings of format:

day       time 1/1/2015  2:30:14 2/1/2015  15:10:40 3/1/2015  8:50:05 

and knowing ggplot2 can bit picky time , date classes, format variables posixct , date follows:

library(ggplot2); library(scales) datetime <- data.frame(date = c("1/1/2015", "2/1/2015", "3/1/2015"),                     time = c("2:30:14", "15:10:40", "8:50:05")) datetime$date <- as.date(datetime$date, format="%m/%d/%y") datetime$time <- as.posixct(datetime$time, format="%h:%m:%s") 

then, creating simple scatter plot of data works fine:

ggplot(datetime, aes(date, time)) +     geom_point() +     xlab("day") +     ylab("time") +     scale_y_datetime(breaks = date_breaks("1 hour"),                       labels = date_format("%h:%m")) 

but, replacing geom_point() geom_bar(stat="identity") create barchart seems result in everloading process , crashing of r:

ggplot(datetime, aes(date, time)) +     geom_bar(stat="identity") +     xlab("day") +     ylab("time") +     scale_y_datetime(breaks = date_breaks("1 hour"),                       labels = date_format("%h:%m")) 

i'm misunderstanding functionality of ggplot2, can please enlighten me going on here?

in ggplot2 barchart's y-scale default starts zero. or, in case of date , time value, start value, 1/1/1970. means bars 45-years long (for time values r apparently sets today date). force ggplot2 use fine scale on period of time: set breaks 1 hour:

scale_y_datetime(breaks = date_breaks("1 hour"),                      labels = date_format("%h:%m")) 

which cause r crash. if use just

ggplot(data, aes(day, time)) +   geom_bar(stat = "identity") 

it work, bars indistinguishable. make bars distinguishable have change y-limits, example time period between 0:00:00 23:59:59. works me:

ggplot(data, aes(day, time)) +   geom_bar(stat = "identity") +   xlab("day") +   ylab("time") +   coord_cartesian(ylim=c(as.posixct("0:0:0", format="%h:%m:%s"),                          as.posixct("23:59:59", format="%h:%m:%s"))) +   scale_y_datetime(breaks = date_breaks("1 hour"),                  labels = date_format("%h:%m")) +   scale_x_date(breaks = pretty_breaks(10))