[R] symbols plot

Joerg van den Hoff j.van_den_hoff at fz-rossendorf.de
Thu Mar 30 09:45:00 CEST 2006

before getting scolded for submitting a (non-)bug report:

when using the 'symbols' function for plotting boxplot data (i.e. using 
'boxplots' symbols), I noted that the x/y-position of the symbols is 
associated with the center of the box.

while this is obviously natural for a usual plotting symbol (say a 
circle or a rectangle), it is probably not desired if one uses the 
'boxplots' symbols: looking at such a plot, probably everyone will 
assume that y-position is that of the median within the box (in other 
words: that one can read off the values of the medians from the y-axis).

the current behaviour is counter-intuitive, I believe, if the 
distributions are asymmetrical (and the median is not centered in it's 
box). (I even think, that such plots are misinterpreted easily: think 
what happens if the median lies very near one of the hinges in one box 
and is centered in another one within the same plot and the medians are 
actually the same)

in short: I think the 'boxplots' should not be centered at the specified 
y-coordinates but rather drawn with a y-coordinate of

y + bxh * (0.5 - bxm)

where bxh and bxm are the second and fifths column of the 'boxplots' 
matrix. in this way, the median position is identical to the specified 

at the very least, I think, the manpage should explicitely state that 
all symbols (including boxplots) are positioned with their geometrical 
center at the specified coordinates.

right or wrong?



More information about the R-help mailing list