Gantt style time line plot (in base R)

Question

I have a dataframe that looks like this:

       person n start end
1         sam 6     0   6
2        greg 5     6  11
3     teacher 4    11  15
4         sam 4    15  19
5        greg 5    19  24
6       sally 5    24  29
7        greg 4    29  33
8         sam 3    33  36
9       sally 5    36  41
10 researcher 6    41  47
11       greg 6    47  53

Where start and end are times or durations (sam spoke from 0 to 6; greg from 6 to 11 etc.). n is how long (in this case # of words) the person spoke. I want to plot this as a time line in base R (I eventually may ask a similar question using ggplot2 but this answer is specific to base R [when I say base I mean the packages that come with a standard install]).

The y axis will be by person and the x axis will be time. Hopefully the final product looks something like this for the data above:

I would like to use base R to make this. I'm not sure how to approach this. My thoughts are to use a dot plot and plot a dotplot but leave out the dots. Then go over this with square end segments. I'm not sure about how this will work since the segments need numeric x and y points to make the segments and the y axis is categorical. Another thought is to convert the factors to numeric (assign each factor a number) and plot as a blank scatterplot and then go over with square end line segments. This could be a powerful tool in my field looking at speech patterns.

I thank you in advance for your help.

PS the argument for square ended line segments is segments(... , lend=2) to save time looking this information up for those not familiar with all the segment arguments.

Answer 1

You say you want a base R solution, but you don't say why. Since this is one line of code in ggplot, I show this anyway.

library(ggplot2)
ggplot(dat, aes(colour=person)) + 
    geom_segment(aes(x=start, xend=end, y=person, yend=person), size=3) +
    xlab("Duration")