On Aug 19, 2009, at 6:02 AM, Michael Kogan wrote:
Unfortunately the matrix(list(),x,y) way seems to have some
limitations. I want to continue working with the matrices which are
saved in the database matrix. But for example the following doesn't
work:
tetrahedron=matrix(c(
0,1,1,1,
1,0,1,1,
1,1,0,1,
1,1,1,0
),nrow=4, byrow=TRUE) # an example matrix
database=matrix(list(),5,5) # create database matrix
database[[4,4]]=list(tetrahedron) # save example matrix in database
matrix
## try to access the first row of the saved example matrix ##
database[[4,4]][1] # prints the whole example matrix
I was surprised that this worked. I would have expected that you would
have used:
database[4,4][[1]] since database is a matrix and generally one
accesses matrix elements
with "[<n>,<m>]" addressing, while the element is a list and would
need "[[<n>]]" addressing.
database[[4,4]][1][1,] # should have printed the first row of the
example matrix, but gives:
So I tried:
database[4,4][[1]][1,]
# [1] 0 1 1 1 ....Success
Error in database[[4, 4]][1][1,] : incorrect number of dimensions
Execution halted
The same happens with database[[4,4]][1,]... Is there any way to
access the saved matrices like "normal" ones?
Thanks,
Michael
jim holtman schrieb:
Is this what you want:
x <- matrix(list(),3,3) # create a matrix of lists
# create matrices for testing
for(i in 1:3){
+ for (j in 1:3){
+ x[[i,j]] <- matrix(runif((i+1) * (j+1)), i+1)
+ }
+ }
x
[,1] [,2] [,3]
[1,] Numeric,4 Numeric,6 Numeric,8
[2,] Numeric,6 Numeric,9 Numeric,12
[3,] Numeric,8 Numeric,12 Numeric,16
x[[2,2]] # extract one of them
[,1] [,2] [,3]
[1,] 0.26722067 0.3823880 0.4820801
[2,] 0.38611409 0.8696908 0.5995658
[3,] 0.01339033 0.3403490 0.4935413
str(x) # structure of the data
List of 9
$ : num [1:2, 1:2] 0.266 0.372 0.573 0.908
$ : num [1:3, 1:2] 0.38 0.777 0.935 0.212 0.652 ...
$ : num [1:4, 1:2] 0.7894 0.0233 0.4772 0.7323 0.6927 ...
$ : num [1:2, 1:3] 0.202 0.898 0.945 0.661 0.629 ...
$ : num [1:3, 1:3] 0.2672 0.3861 0.0134 0.3824 0.8697 ...
$ : num [1:4, 1:3] 0.2448 0.0707 0.0995 0.3163 0.5186 ...
$ : num [1:2, 1:4] 0.206 0.177 0.687 0.384 0.77 ...
$ : num [1:3, 1:4] 0.186 0.827 0.668 0.794 0.108 ...
$ : num [1:4, 1:4] 0.258 0.4785 0.7663 0.0842 0.8753 ...
- attr(*, "dim")= int [1:2] 3 3
On Tue, Aug 18, 2009 at 4:48 AM, Michael
Kogan<michael.ko...@gmx.net> wrote:
Hi,
I'm new to programming, new to R and even new to mailing lists so
please be
patient with me. I need to manage many matrices generated by an R
program.
These matrices have different dimensions and I'd like to group
them somehow.
The best way would be to have a big matrix (let's call it
database) where
every element database[x,y] consists of a list of matrices that
all have the
dimensions ncol(matrix1)=x and nrow(matrix1)=y. So those matrices
have to be
embedded into lists and the lists have to be embedded in the big
database
matrix. If I simply try
database=matrix(0,10,10)
database[4,4]=c(matrix1,matrix2)
I get
Error in database[4, 4] = c(matrix1, matrix2) :
number of items to replace is not a multiple of replacement
length
Execution halted
which makes sense of course... Is there any possibility to make
this work?
Or maybe there is a better way to organize those matrices?
Regards,
Michael
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
R-help@r-project.org 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.
