spconvert

Purpose

Convert external form of a sparse matrix.

Synopsis

S = spconvert(D)

Description

The load and save commands handle sparse matrices, so there is no need for a special sparse load or save command. However, conversion between the external form and internal form of a sparse matrix is needed after loading from an ASCII text file.

S = spconvert(D) converts a matrix D with rows containing [i,j,s] or [i,j,r,s]to the corresponding sparse matrix. D must have an nnz or nnz+1 row and three or four columns. Three elements per row generate a real matrix and four elements per row generate a complex matrix. A row of the form [m n 0] or [m n 0 0] anywhere in D can be used to specify size(S). If D is already sparse, no conversion is done, so spconvert can be used after D is loaded from either a MAT-file or an ASCII file.

Examples

Suppose the ASCII file uphill.dat contains

1    1    1.000000000000000
1    2    0.500000000000000
2    2    0.333333333333333
1    3    0.333333333333333
2    3    0.250000000000000
3    3    0.200000000000000
1    4    0.250000000000000
2    4    0.200000000000000
3    4    0.166666666666667
4    4    0.142857142857143
4    4    0.000000000000000
Then the statements

load uphill.dat
H = spconvert(uphill)
recreate sparse(triu(hilb(4))), possibly with roundoff errors. In this case, the last line of the input file is not necessary because the earlier lines already specify that the matrix is at least 4-by-4.

(c) Copyright 1994 by The MathWorks, Inc.