[R] problems with plot.data.frame

[Prof Brian Ripley]

On Thu, 31 Aug 2006, Monica Pisica wrote:

> Hi list,
> 
> I have a question about 'plot'. I am trying to plot values registered every 
> month - or every other month. If i build a data.frame called mydata like 
> this (as an example)
> 
> jan   3   1   7
> mar  2   4   2
> may 1   3   2
> jul    3   7   4
> sep  5   2   3
> nov  3   1   5

This has no column names, so it looks like this is 3 columns with row 
names.  I think it is actually four columns, but it would never print like 
that.

Quite likely then the first column is a factor with levels in alphabetical 
order.  If I copy your layout and do

> read.table("clipboard") -> A
> A
   V1 V2 V3 V4
1 jan  3  1  7
2 mar  2  4  2
3 may  1  3  2
4 jul  3  7  4
5 sep  5  2  3
6 nov  3  1  5

> levels(A[[1]])
[1] "jan" "jul" "mar" "may" "nov" "sep"

and you seem to want

a <- as.character(A[[1]])
A[[1]] <- factor(a, levels=a)

and then

plot.default(A[c(1,3)])

(You are showing a boxplot, since you are plotting a numeric variable 
against a factor.)

> 
> and use the command line:
> 
> plot(mydata[c(1,3)])
> 
> I get a graph that has on the x axis my months in alphabetical order - which 
> i don't want, and instead of points i have thick horizontal lines. I've 
> tried everything i could and understood from the R help files to give me 
> points and on x axis the month in my order instead of alpha order. No 
> success. What is the trick?
> 
> I fixed the month order by using numerals in front of them like 01, 03, ... 
> etc, but this is not an elegant solution.
> 
> Any help will be much appreciated.
> 
> Monica
> 
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595