[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
>
>
>