MATLAB Application Program Interface Reference Help Desk

mxSetJc

Purpose

Set the jc array of a sparse mxArray

C Syntax

Arguments

array_ptr

Pointer to a sparse mxArray.

jc

Pointer to the jc array.

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:

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

The contents of the ir, jc, and pr arrays are

Subscript

ir

pr

jc

Comment

(2,1)

1

1

0

Column 1 contains 2 entries, at ir[0],ir[1]

(5,1)

4

1

2

Column 2 contains 1 entry, at ir[2]

(3,2)

2

1

3

Column 3 contains 3 entries, at ir[3],ir[4], ir[5]

(2,3)

1

2

6

There are 6 nonzero elements.

(5,3)

4

1

 

 

(6,3)

5

1

 

 

Now onto a much sparser mxArray. Consider an 8,000 element sparse mxArray named Spacious containing only 3 nonzero elements. The ir, pr, and jc arrays contain

Subscript

ir

pr

jc

Comment

(73,2)

72

1

0

Column 1 contains 0 entries

(50,3)

49

1

0

Column 2 contains 1 entry, at ir[0]

(64,5)

63

1

1

Column 3 contains 1 entry, at ir[1]

 

 

 

2

Column 4 contains 0 entries.

 

 

 

2

Column 5 contains 1 entry, at ir[3]

 

 

 

3

Column 6 contains 0 entries.

 

 

 

3

Column 7 contains 0 entries.

 

 

 

3

Column 8 contains 0 entries.

 

 

 

3

There are 3 nonzero elements.

Example

See the example on the mxSetNzmax reference page.

See Also

mxGetIr, mxGetJc, mxSetIr



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