[R] Rotating the x-axis labels of a barplot

[Marc Schwartz]

On Apr 16, 2011, at 11:50 AM, Peter Ehlers wrote:

> On 2011-04-16 09:36, Sascha Vieweg wrote:
>> On 11-04-16 15:04, Josh B wrote:
>> 
>>> Dear listserv,
>>> 
>>> Here is my latest formatting problem. I would like to rotate the x-axis labels
>>> by 45 degrees on a _barplot_. Apparently this is slightly different from the
>>> example given in the R FAQ, which is for rotating the x-axis labels on a
>>> scatterplot
>>> (http://cran.r-project.org/doc/FAQ/R-FAQ.html#How-can-I-create-rotated-axis-labels_003f).
>>> 
>>> 
>>> I have adapted that code, as best I could, and here is what I have come up with
>>> so far:
>>> 
>>> x<- c(4, 1, 1, 1)
>>> barplot(x, space = 0)
>>> #the "space = 0" argument, above, just reflects my personal preference for
>>> having no space between the bars
>>> text(1:4, par("usr")[3] - 0.025, srt = 45, adj = 1, labels = c("<  750",
>>> "750-1000", "1000-1250",">  1250"), xpd = TRUE, font = 2)
>>> 
>>> The graph this generates is pretty close to what I want, but here's where I'm
>>> stuck: How do I move the x-axis labels to the _center_ of each bar? Right now,
>>> they line up with the right-side of each bar.
>> 
>> Try to set the parameter: adj=.5 (see ?par). HTH, *S*
>> 
> 
> That won't work (try it).
> 
> Use
> 
>  text(1:4-0.5, ....)
> 
> Peter Ehlers


Actually, the key is knowing that barplot() returns the bar midpoints (See the Value section of ?barplot).

Thus:

x <- c(4, 1, 1, 1)

mp <- barplot(x, space = 0)

text(mp, par("usr")[3] - 0.025, srt = 45, adj = 1, 
     labels = c("< 750", "750-1000", "1000-1250", "> 1250"), 
     xpd = TRUE, font = 2)

HTH,

Marc Schwartz