R - ggplot2 - plot regions as lines

Question

I have a dataframe with regions and values. Here's a toy example.

Start    End    Value
1        100     2
100      200     3
300      400     2
400      500     1

What I'd like to do is create a plot where each region (in line 1, that is Start=1 , End=100 ) is plotted on the x, and the Value is on the y. And preferably, I'd like to use ggplot2. I have many different applications for this, but they all boil down to this one question.

What I'd end up with is a plot with flat (slope=0) lines for each region. Here's an example of the type of plot if you ignore the points, and just focus on the lines .

Copy number plot

In words, you would have one plot, with (for the toy data) a line from x=1-100 with ay value of 2, then lines (x,y): (100-200, 3)(300-400, 2)(400-500, 1)

Answer 1

You can use geom_segment to draw line segments. See ?geom_segment for details.

ggplot(df) + 
    geom_segment(aes(x = Start, xend = End, y = Value, yend = Value))

Using this data:

df = structure(list(Start = c(1L, 100L, 300L, 400L), End = c(100L, 
200L, 400L, 500L), Value = c(2L, 3L, 2L, 1L)), .Names = c("Start", 
"End", "Value"), class = "data.frame", row.names = c(NA, -4L))

You should probably check out some introductory ggplot2 resources. There are lots of suggestions in the ggplot2 tag wiki .