Saving a multi-dimensional matrix to a file

Question

I have a 6D matrix (it may eventually get larger) that I would like to save as a txt, csv or xcel file. I want to do this because the output is too big for the console window and I just want to be able to look over the data quickly before analysing it. Also, my supervisor doesn't work with R so if I want him to look at the data I need to be able to export it out of R.

What I want is to be able to see the data, with headings telling me which part of the matrix I'm in. i.e.

, , 1, 5, 6, 5

Alternatively the data could be rearranged into a table provided that each row of the data set specifies which part of the matrix it was in. e.g. a column per dimension of the matrix.

So far I've tried write.matrix, write.csv, and write.big.matrix with no success.

The error message I get for write.big.matrix is:

Error in (function (classes, fdef, mtable)  : 
  unable to find an inherited method for function ‘write.big.matrix’ for signature ‘"array", "character"’

Many thanks for your help.

Answer 1

Suggestions:

1. Get your supervisor to work with R

2. Use the ncdf package to write a NetCDF file, which can be multi-dimensional (its often used for space-time data which is 4D)

3. Use the reshape2 package to convert the array into a i,j,k,l,m,n,value formatted data frame (where i to n are your dimension indexes, and value is the value of A[i,j,k,l,m,n]. Here's a 3-dimensional example:

   a=array(sample(24),c(2,3,4))

a is now a 3d array:

> a
, , 1

     [,1] [,2] [,3]
[1,]   23   21   20
[2,]   22    7   14

, , 2

     [,1] [,2] [,3]
[1,]   11    9    5
[2,]   12    6   17

, , 3

     [,1] [,2] [,3]
[1,]   16    3   24
[2,]    1   10    4

, , 4

     [,1] [,2] [,3]
[1,]    2   19    8
[2,]   18   15   13

Its then a one-liner:

> require(reshape2)
> melt(a)
   Var1 Var2 Var3 value
1     1    1    1    23
2     2    1    1    22
3     1    2    1    21
4     2    2    1     7
5     1    3    1    20
6     2    3    1    14
7     1    1    2    11
...
17    1    3    3    24
18    2    3    3     4
19    1    1    4     2
20    2    1    4    18
21    1    2    4    19
22    2    2    4    15
23    1    3    4     8
24    2    3    4    13

to get something you can write.table as a CSV file for your Excel-loving supervisor.