Re: [R] matrix and error in points, plot ?

2005-01-03 Thread Prof Brian Ripley 
You have forgotten drop=FALSE in mat[1,]: take a look at what it produces.
See ?Extract for more details.
On Mon, 3 Jan 2005, Patrick Giraudoux H wrote:
Would a specialist of the point or plot functions try the following:
mat-matrix(c(1.836767,4.025989,0.6396777,0.376),ncol=2)
plot(mat)
points(mat[1,],col=red)
..A lag appears on x for mat [1,1] between the two displays.
I wonder if this example may be due to a bug or to the mis-use of a matrix in 
the plot() points()  functions. In case of mise-use which kind can it be?
Not using a matrix at all!
--
Brian D. Ripley,  [EMAIL PROTECTED]
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, UKFax:  +44 1865 272595
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Re: [R] matrix and error in points, plot ?

2005-01-03 Thread Uwe Ligges 
Patrick Giraudoux H wrote:
Hi,
Would a specialist of the point or plot functions try the following:
mat-matrix(c(1.836767,4.025989,0.6396777,0.376),ncol=2)
plot(mat)
points(mat[1,],col=red)
..A lag appears on x for mat [1,1] between the two displays.
I wonder if this example may be due to a bug or to the mis-use of a 
matrix in the plot() points()  functions. In case of mise-use which kind 
can it be?

It's misuse:
For a matrix, the first column is interpreted as the x-coordinates, the 
second one as y-coordinates.

For a vector (mat[1,] is a (1D) vector!) plot/points plots the values 
(as y-coordinates) against their index (1:2 in this case, where 1 is not 
visible in the plot).

You can use
  points(mat[1,,drop=FALSE], col=red)
in order not to drop dimensions, so mat[1,,drop=FASLE] is still a 
2-column matrix.

Uwe Ligges

I am working with R 2.0.1 and Windows XP.
Cheers,
Patrick Giraudoux
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