How to create bar plot for characters in R

Question

I have a data frame that looks like this

head(data1, 30)
      date                cur.gas
1  2015-01-01 00:00:45      RD
2  2015-01-01 00:02:45      RD
3  2015-01-01 00:04:45      RD
4  2015-01-01 00:06:45      RD
5  2015-01-01 00:08:45      RD
6  2015-01-01 00:10:45      RD
7  2015-01-01 00:12:45      RD
8  2015-01-01 00:14:45      RD
9  2015-01-01 00:16:45      RD
10 2015-01-01 00:18:45      RD
11 2015-01-01 00:20:45      RD
12 2015-01-01 00:22:45      RD
13 2015-01-01 00:24:45      RD
14 2015-01-01 00:26:45      RD
15 2015-01-01 00:28:45      RD
16 2015-01-01 00:30:45      RD
17 2015-01-01 00:40:45      BL
18 2015-01-01 00:42:45      BL
19 2015-01-01 00:44:45      BL
20 2015-01-01 00:46:45      BL
21 2015-01-01 00:48:45      BL
22 2015-01-01 00:50:45      BL
23 2015-01-01 00:52:45      BL
24 2015-01-01 00:54:45      BL
25 2015-01-01 00:56:45      BL
26 2015-01-01 00:58:45      BL
27 2015-01-01 01:00:45      BL
28 2015-01-01 01:46:45      RD
29 2015-01-01 01:50:45      RD
30 2015-01-01 01:52:45      RD

Where the cur.gas column indicated which line (Red (RD) or blue (BL)) is feeding the sample into the analyser. I want to create horizontal bar plot from this data that would show me the colour corresponding to the current line (red and blue).

I have tried using ggplot:

ggplot(data=data1, aes(x=0.1, y = date, col=cur.gas)) +
geom_bar(stat = "identity", width = 0.1) + 
coord_flip() +
scale_fill_manual(values = c("red","blue")) +
theme(text = element_text(size = 10), axis.title = element_blank(), axis.text  = element_blank(),
axis.ticks = element_blank())

And the output plot looks like this:

Which looks horible, and the colours are wrong (the legend gives red colour for BL and blue for RD).

Then I tried the barplot function:

attach(data1)
barplot(date,names.arg=cur.gas, horiz = TRUE, col = c("blue", "red"), legend = rownames(data1$cur.gas))

and I got this error:

Error in barplot.default(date, names.arg = cur.gas, horiz = TRUE, col = c("blue",  : 
'height' must be a vector or a matrix

I'm lost now. What should I do? Thanks a lot1

Answer 1

What barplot wants is INTERVALS.

data[,"end_date"] <- c(data[-1,1], as.POSIXct("2015-01-01 01:54:45")) # I deciced a last value arbitrarily
data[,"interval"] <- difftime(data$end_date, data$date)
difftime(data$date[1], tail(data$end_date, n=1), units="min") # total 114 min

barplot(matrix(data$interval, ncol=1), horiz=T, col=c(2,4)[data$cur.gas], axes=F)
axis(1, at=seq(0,114,10), las=2, cex.axis=0.8,  # If you don't need border, add border=NA
     labels=format(seq(data[1,1], tail(data$end_date, n=1), by="10 min"),"%H:%M:%S"))

But it is more easy to use geom_rect() (this code needs end_date)

ggplot(data) + 
  geom_rect(aes(xmin=date, xmax=end_date, ymin=0, ymax=1, fill=cur.gas), colour="black") +
  theme(axis.text.y=element_blank(), axis.ticks.y=element_blank()) + labs(x="time")
    # if you don't need border, delete colour="black".