[R] ggplot axis limit

[Brian Diggs]

On 3/16/2012 10:29 AM, mdvaan wrote:
> Hi,
>
> This is probably an easy one, but I am new to ggplot2 and cannot find an
> answer online.

Just so you know, there is a mailing list devoted to ggplot2. You can 
subscribe and view messages at 
https://groups.google.com/forum/?fromgroups#!forum/ggplot2

> I am bar plotting values of 10 groups. These values are all within a 90-100
> range, so I would like leave out the area of the bars below 90. If I say
> "graph + scale_y_continuous(limit=c(90, 100))", it does limit the axis but
> the bars disappear completely. Any solution here?

You want to zoom the axes, not limit the scales (very different concepts 
in ggplot2).  You need

graph + coord_cartesian(ylim=c(90,100))

Now, I'm going to tell you that you shouldn't do that.  Bars go to 0. 
That is because the information in the bar (visually) is in its length. 
By cutting the bars off, you are distorting them. Effectively, this is 
what you did with the scale call; you said to throw out any data outside 
the range of 90-100. Since the bottom of the bar was below that, it got 
thrown out, so the rest of the bar got thrown out as well.

If you only want to show the 90-100 range, consider just points.

> Thanks a lot!
>
> Mathijs


-- 
Brian S. Diggs, PhD
Senior Research Associate, Department of Surgery
Oregon Health & Science University