External Interfaces Reference |
Set jc
array of sparse mxArray
C Syntax
Arguments
array_ptr
Pointer to a sparse mxArray
.
Description
Use mxSetJc
to specify a new jc
array for a sparse mxArray
. The jc
array is an integer array having n+1
elements where n
is the number of columns in the sparse mxArray
. The values in the jc
array have the meanings:
jc[j]
is the index in ir
, pr
(and pi
if it exists) of the first nonzero entry in the jth column.
jc[j+1]-1
is the index of the last nonzero entry in the jth column.
jc
[number of columns + 1
] is equal to nnz
, which is the number of nonzero entries in the entire spare mxArray
.
The number of nonzero elements in any column (denoted as column C) is
For example, consider a 7-by-3 sparse mxArray
named Sparrow
containing six nonzero elements, created by typing
Sparrow = zeros(7,3); Sparrow(2,1) = 1; Sparrow(5,1) = 1; Sparrow(3,2) = 1; Sparrow(2,3) = 2; Sparrow(5,3) = 1; Sparrow(6,3) = 1; Sparrow = sparse(Sparrow);
The contents of the ir
, jc
, and pr
arrays are:
Subscript |
ir |
pr |
jc |
Comment |
(2,1) |
1 |
|
|
|
(5,1) |
4 |
|
|
|
(3,2) |
2 |
|
|
|
(2,3) |
1 |
|
|
|
(5,3) |
4 |
|
|
|
(6,3) |
5 |
|
|
|
As an example of a much sparser mxArray
, consider an 8,000 element sparse mxArray
named Spacious
containing only three nonzero elements. The ir
, pr
, and jc
arrays contain:
Subscript |
ir |
pr |
jc |
Comment |
(73,2) |
72 |
|
|
|
(50,3) |
49 |
|
|
|
(64,5) |
63 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
3 |
|||
|
3 |
|||
|
3 |
Examples
See mxsetdimensions.c
in the mx
subdirectory of the examples
directory. For an additional example, see explore.c
in the mex
subdirectory of the examples
directory.
See Also
mxSetIr | mxSetLogical (Obsolete) |
© 1994-2005 The MathWorks, Inc.