[R] barplot default colors

[Marc Schwartz]

>-----Original Message-----
>From: r-help-admin at stat.math.ethz.ch 
>[mailto:r-help-admin at stat.math.ethz.ch] On Behalf Of Liaw, Andy
>Sent: Wednesday, February 05, 2003 7:00 AM
>To: 'r-help at stat.math.ethz.ch'
>Subject: [R] barplot default colors
>
>
>Dear R-help,
>
>Can some one explain why barplot() uses changing colors in the 
>bars by default?  I should think that most of the time when 
>people draw barplots, they want the bars to be in the same 
>color.  (At least that's what I'd expect.  The first time I 
>used barplot() in R, I was shocked to see the
>colors.)  As an example, one example in ?layout draws a 
>scatterplot with histograms drawn on the margins.  The 
>histograms were drawn by barplot(), and, IMHO, look rather 
>hideous in the colors.
>
>Regards,
>Andy
>
>Andy I. Liaw, PhD
>Biometrics Research          Phone: (732) 594-0820
>Merck & Co., Inc.              Fax: (732) 594-1565
>P.O. Box 2000, RY84-16            Rahway, NJ 07065
>mailto:andy_liaw at merck.com

Andy,

This is an extrapolation beyond known data by me, but I would suspect
that one plausible reason is that since barplot can do grouped bars
and stacked bars, the original author decided to set a single default
multiple color vector for all cases. 

This would be one approach rather than checking to see what type of
barplot was being drawn and using a single color for the scenario you
are using or a multiple color vector for grouped/stacked bars.

It is obviously easy enough to add 'col = "color"' to the barplot()
arguments to use a single color of your choosing or an alternate
multiple color vector.

To change the default behavior now would likely break other code in
use.

My two cents....

Regards,

Marc Schwartz