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

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