[R] Help barplots

[Peter Ehlers]

On 2010-06-01 5:01, khush ........ wrote:
> Dear All,
>
> I am newbie to R, and I wanted to plot a barplots with R and in such a way
> that It will also show me position which I can plot on the bar line.
>
> Here is my code that I am using to plot,
>
>> chromosome<- c(40.2, 35.6, 36.1, 29.6, 31, 29.6, 31, 29.4, 28.2, 23, 23,
> 28.2)
>> barplot (chromosome, col="purple", xlab="Oryza sativa Chromosomes", border
> = NA, space = 5, ylim = c(0,45))
>
> I wanted to mark the position say on chromosome 1 (40.2) I need to mark 10.2
> and on other also.
> I also want to set the scale of y axis from 0,5,10,15,20,25,30,35,40,45 i.e
> gap of 5 instead of 10.
>
> please help me to solve my query....gurus.
>

If I understand correctly, maybe you want something like this:

# save the x-locations of the bars in a vector bp;
# use that to put marks on the bars with points();
# omit the default y-axis with yaxt = "n" or, as Petr
# showed, with axes = FALSE;

  bp <- barplot(chromosome, border = NA, space = 5,
                ylim = c(0, 45), yaxt = "n")
  points(bp[1], 10.2, pch = 4, cex = 2)

# add the y-axis:
  axis(2, at = seq(0, 45, 5), las = 1)

#(you might want to add: box(bty = "l")

Instead of points(), you could use segments() to place
horizontal marks.

   -Peter Ehlers

>
> Thank you
> Jeet
>