Re: [R] Error during wrapup: incorrect number of dimensions

[Peter Ehlers]

On 2012-03-26 12:57, Sam Steingold wrote:

when subsetting a matrix results in a single row, it is converted to a
vector, not a matrix.
how do I avoid this?

Check ?"[" and note the 'drop=' argument.

Peter Ehlers

1. __GOOD__

edges<- get.edges(g,E(g))
edges

       [,1] [,2]
  [1,]    0    2
  [2,]    0    3
  [3,]    0    4
  [4,]    0    5
  [5,]    1    1
  [6,]    0    4
  [7,]    0    6
  [8,]    0    7
  [9,]    0    8
[10,]    0    9
[11,]    0    5
[12,]    0   10
[13,]    0   11
[14,]    0   12
[15,]    0   11
[16,]    0   13
[17,]    0   14
[18,]    0   15
[19,]    0   16
[20,]    1   17
[21,]    1   11
[22,]    0   11

loops<- edges[,1] == edges[,2]
loopless<- edges[!loops,]
loopless

loopless
       [,1] [,2]
  [1,]    0    2
  [2,]    0    3
  [3,]    0    4
  [4,]    0    5
  [5,]    0    4
  [6,]    0    6
  [7,]    0    7
  [8,]    0    8
  [9,]    0    9
[10,]    0    5
[11,]    0   10
[12,]    0   11
[13,]    0   12
[14,]    0   11
[15,]    0   13
[16,]    0   14
[17,]    0   15
[18,]    0   16
[19,]    1   17
[20,]    1   11
[21,]    0   11

unique(loopless[,1])

[1] 0 1

2. __BAD__

edges

      [,1] [,2]
[1,]    0    1
[2,]    0    0
Browse[1]>  edges[!loops,]
[1] 0 1

why is it a vector, not a matrix?

Browse[1]>  loopless
[1] 0 1
Browse[1]>  loopless[,1]
Error during wrapup: incorrect number of dimensions

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