Re: Importing a sparse matrix to Octave

[Jaroslav Hajek]

On Fri, Jul 24, 2009 at 9:24 PM, John W. Eaton<address@hidden> wrote:
> On 24-Jul-2009, Chong Yidong wrote:
>
> | "John W. Eaton" <address@hidden> writes:
> |
> | >   # name: s
> | >   # type: sparse complex matrix
> | >   # nnz: 70
> | >   # rows: 10
> | >   # columns: 10
> | >   1 1 (0,1.145193428282681)
> | >   2 1 (0,0.5663270399606521)
> | >   3 1 (0,0.007270909230606313)
> | >   4 1 (0,0.1480797228543177)
> | >   5 1 (0,0.2478795113138578)
> | >   ...
> | >
> | > The first column is the row index, the second is the column index, and
> | > the third is the corresponding value (real,complex).  The number of
> | > elements must match the value of NNZ.  To load this file into Octave,
> | > use the load command.
> |
> | Thanks.  However, this method doesn't seem to work properly:
> |
> | # name: s
> | # type: sparse complex matrix
> | # nnz: 3
> | # rows: 10
> | # columns: 10
> | 1 1 (0,1.14)
> | 3 6 (0,0.56)
> | 6 2 (0.1,0.0)
> |
> | octave:1> load "foo.dat"
> | octave:2> s
> | s =
> |
> | Compressed Column Sparse (rows = 10, cols = 10, nnz = 3)
> |
> |   (1, 1) ->  0.00000 + 1.14000i
> |   (3, 2) ->  0.00000 + 0.56000i
> |   (6, 2) ->  0.10000 + 0.00000i
> |
> | The second line seems to be assigned to the wrong entry.  Is this a bug?
> | I'm using Octave 3.0.1, as distributed by Ubuntu.
>
> Oops, there was one detail I wasn't aware of.  You must group the
> elements by column.  So change your file to
>
>  # name: s
>  # type: sparse complex matrix
>  # nnz: 3
>  # rows: 10
>  # columns: 10
>  1 1 (0,1.14)
>  6 2 (0.1,0.0)
>  3 6 (0,0.56)
>
> and I think it should work.
>

No, not yet. A futher requirement is that the row indices should be
sorted (for a certain column index).

-- 
RNDr. Jaroslav Hajek
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz