[R] Populate matrix from data.frame
Dear all,
I have a data frame
a - data.frame(cbind(x=c('a','a','a','b','c'),
y=c('a','b','c','d','e'),z=c(1,2,3,4,5)))
a
x y z
1 a a 1
2 a b 2
3 a c 3
4 b d 4
5 c e 5
and a matrix
mm - matrix(0,5,5)
colnames(mm) - c('a','b','c','d','e')
rownames(mm) - c('a','b','c','d','e')
mm
a b c d e
a 0 0 0 0 0
b 0 0 0 0 0
c 0 0 0 0 0
d 0 0 0 0 0
e 0 0 0 0 0
How to populate matrix in a way that first column of data frame 'a'
correspond to rownames(mm), second column to colnames(mm) and the third
column is the element of matrix 'mm'?
Thanks in advance,
Andrej
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Populate matrix from data.frame
On Thu, 28 Jun 2007, Andrej Kastrin wrote:
Dear all,
I have a data frame
a - data.frame(cbind(x=c('a','a','a','b','c'),
y=c('a','b','c','d','e'),z=c(1,2,3,4,5)))
a
x y z
1 a a 1
2 a b 2
3 a c 3
4 b d 4
5 c e 5
and a matrix
mm - matrix(0,5,5)
colnames(mm) - c('a','b','c','d','e')
rownames(mm) - c('a','b','c','d','e')
mm
a b c d e
a 0 0 0 0 0
b 0 0 0 0 0
c 0 0 0 0 0
d 0 0 0 0 0
e 0 0 0 0 0
How to populate matrix in a way that first column of data frame 'a'
correspond to rownames(mm), second column to colnames(mm) and the third
column is the element of matrix 'mm'?
mm[cbind(a$x, a$y)] - a$z
Please read about the forms of indexing matrices in 'An Introduction to
R'.
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UKFax: +44 1865 272595
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Populate matrix from data.frame
You need some caution with Brian's solution as it
depends on the matrix being in the same order as
the factors in the data frame.
a - data.frame(cbind(x=c('a','a','a','b','c'),
y=c('a','b','c','d','e'),z=c(1,2,3,4,5)))
mm - matrix(0,5,5)
colnames(mm) - c('a','b','c','d','e')
rownames(mm) - c('a','b','c','d','e')
pp - mm[5:1, 5:1]
mm[cbind(a$x, a$y)] - a$z # desired result
pp[cbind(a$x, a$y)] - a$z # not desired result
It would be nice if the following worked:
mm[cbind(as.character(a$x), as.character(a$y))] - a$z
Patrick Burns
[EMAIL PROTECTED]
+44 (0)20 8525 0696
http://www.burns-stat.com
(home of S Poetry and A Guide for the Unwilling S User)
Prof Brian Ripley wrote:
On Thu, 28 Jun 2007, Andrej Kastrin wrote:
Dear all,
I have a data frame
a - data.frame(cbind(x=c('a','a','a','b','c'),
y=c('a','b','c','d','e'),z=c(1,2,3,4,5)))
a
x y z
1 a a 1
2 a b 2
3 a c 3
4 b d 4
5 c e 5
and a matrix
mm - matrix(0,5,5)
colnames(mm) - c('a','b','c','d','e')
rownames(mm) - c('a','b','c','d','e')
mm
a b c d e
a 0 0 0 0 0
b 0 0 0 0 0
c 0 0 0 0 0
d 0 0 0 0 0
e 0 0 0 0 0
How to populate matrix in a way that first column of data frame 'a'
correspond to rownames(mm), second column to colnames(mm) and the third
column is the element of matrix 'mm'?
mm[cbind(a$x, a$y)] - a$z
Please read about the forms of indexing matrices in 'An Introduction to
R'.
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
