geom_bar not showing every values - r

Question

I want to draw a bar plot, with ggplot and geom_bar, but it seems that the behavior of geom_bar is not consistent. I don't understand why.
My data is a time series of precipitations:
library(ggplot2)
library(data.table)
library(lubridate)
set.seed(42)
dt1 <- data.table(dateHeure=seq(ymd_hms("2014-06-04 13:30:00"),
ymd_hms("2014-10-20 08:30:00"), by='1 hour'),
rain=sample(c(rep(5,15), rep(10,15), rep(20,10),
rep(30, 5), 40, rep(0, 3262))))
Then i plot it, and not all the data appears... Why is some data missing?
ggplot(data=dt1)+
geom_bar(aes(x=dateHeure, y=rain),
stat="identity",
fill="blue") # doesn't work!
But if i add the variable color in aes, then the plot is correct!
ggplot(data=dt1)+
geom_bar(aes(x=dateHeure, y=rain, color="rain"),
stat="identity",
width=0.2) # work properly
So someone know why geom_bar doesn't work properly without color? Because i can't rely on it if sometimes not all the data is correctly plotted...
thanks!
edit: to respond to #eipi10, i added the plots. The strange thing is that when i resize the plot window in the first case, the data which is plotted changes!

Answer 1

Based on the edit to your question, I think I know what's happening: In the first plot, you use fill="blue". But the bin widths are very small compared to the overall range of the x-axis. This results in very, very thin vertical bars--so thin that you can't see some of them on your screen, but they appear when you expand the physical width of the plot.
On the other hand, in your second plot you used colour="rain", which adds a border to each bar, making each bar thicker, so they are visible, even when the physical width of the plot is relatively small.
Try adding colour="blue"(or "red" or whatever) to your first plot and I think you'll see all the bars, even without resizing. On the other hand, try changing colour="rain" to fill="rain" on your second plot and see if that creates the "disappearing data" effect on your second plot.
UPDATE: In response to your comment, you can use the colour parameter and then set the line width to get exactly the bar thickness you want, so you don't really need fill. For example:
ggplot(data=dt1)+
geom_bar(aes(x=dateHeure, y=rain),
stat="identity",
colour="blue", lwd=0.5)
Just set lwd (line width) to a value that gives you the bar-width you want. And, of course, you can also change the colour as well.