[R] Boxplot with full x-range

[Maura Melis]

Hi all,

I'm new to R, and have the following problem:

I wish to draw a boxplot of simple data in two columns.   The x-axis 
(taken from first column) is grouped to intervals (using 'cut').
These intervals serve as x-value to the boxplot, and the data from the 
second column are the y-values.

The problem is that I want to give an impression of the trend of the data 
in the x-range.  However, when an interval on the x-axis contains no 
y-data, no box is drawn, and the plot becomes 'narrower' in the 
x-direction, giving a wrong impression of the trend of the y-value.

What I want is that no box is drawn for emtpy interval, but some X-space 
is kept open.  In other words, I want ALL interval to be drawn, including 
the empty ones.

Example scenario:

data.dat:
0.1 5
0.15 4.5
0.3 2
0.31 2.2
0.5 1
0.55 1.1
0.56 1.15
0.7 0.5
0.9 0.1


> mydata <- read.table("data.dat")
> attach(mydata)
> cats = cut( V1, breaks=(0:10)*.1)
> symmary( cats )

(0,0.1] (0.1,0.2] (0.2,0.3] (0.3,0.4] (0.4,0.5] (0.5,0.6] (0.6,0.7] 
(0.7,0.8]
         1         1         1         1         1         2         
1         0
(0.8,0.9]   (0.9,1]
         1         0

## notice two intervals with zero elements

>  boxplot( V2 ~ cats )  ## this draws the boxplot, and just ignores the 
> empty intervals

Any help would be appreciated,

tnx

Piet


(running R1.7.0 on SUSE linux 8.1, AMD Athlon)


---
Piet van Remortel
Belgium
pvremortATvub.ac.be