spmax
Below is a demonstration of the features of the spmax function
Contents
clear; close all; clc;
Syntax
[maxVal,maxInd]=spmax(A,B,dim,nanflag,logicRelevant,nanOut);
Description
This function is like the max function but is designed for sparse arrays. In particular it allows one to "ignore zeros" in the determination of the maxima.
Examples
Create example matrix
i=[2 1 1 2 2 3 3 4 4 5 5 5 6 6 7 8];
j=[1 1 2 3 4 5 6 7 8 9 10 11 12 13 13 13];
s=[-1 3 1 2 -1 1 -2 5 5 -1 0 2 3 10 11 NaN];
siz=max([i(:);j(:)]+1)*ones(1,2);
A=sparse(i,j,s,siz(1),siz(2),numel(s));
A=A+A';
full(A) % View matrix
L=sparse(i,j,1,siz(1),siz(2),numel(s));
logicRelevant=(L+L')>0;
ans =
Columns 1 through 13
6 0 0 0 0 0 0 0 0 0 0 0 0
0 0 2 -1 0 0 0 0 0 0 0 0 0
0 2 0 0 1 -2 0 0 0 0 0 0 0
0 -1 0 0 0 0 5 5 0 0 0 0 0
0 0 1 0 0 0 0 0 -1 0 2 0 0
0 0 -2 0 0 0 0 0 0 0 0 3 10
0 0 0 5 0 0 0 0 0 0 0 0 11
0 0 0 5 0 0 0 0 0 0 0 0 NaN
0 0 0 0 -1 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 2 0 0 0 0 0 0 0 0
0 0 0 0 0 3 0 0 0 0 0 0 0
0 0 0 0 0 10 11 NaN 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0
Column 14
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Compute maxima allong a certain direction (while omit nan is default)
amaxRows=spmax(A,[],1); full(amaxRows) amaxColumns=spmax(A,[],2); full(amaxColumns)
ans =
Columns 1 through 13
6 2 2 5 2 10 11 5 -1 0 2 3 11
Column 14
0
ans =
6
2
2
5
2
10
11
5
-1
0
2
3
11
0
Including nans
amaxRows=spmax(A,[],1,'includenan'); full(amaxRows) amaxColumns=spmax(A,[],2,'includenan'); full(amaxColumns)
ans =
Columns 1 through 13
6 2 2 5 2 10 11 NaN -1 0 2 3 NaN
Column 14
0
ans =
6
2
2
5
2
10
11
NaN
-1
0
2
3
NaN
0
Computing maxima across all desired relevant entries (including "relevant/real zeros")
amaxRows=spmax(A,[],1,'omitnan',logicRelevant); full(amaxRows) amaxColumns=spmax(A,[],2,'omitnan',logicRelevant); full(amaxColumns)
ans =
Columns 1 through 13
6 2 2 5 2 10 11 5 -1 0 2 3 11
Column 14
0
ans =
6
2
2
5
2
10
11
5
-1
0
2
3
11
0
Computin maxima across all desired relevant entries and output NaN where the sparse array only contains "non-relevant or non-real" zeros.
nanOut=1; amaxRows=spmax(A,[],1,'omitnan',logicRelevant,nanOut); full(amaxRows) amaxColumns=spmax(A,[],2,'omitnan',logicRelevant,nanOut); full(amaxColumns)
ans =
Columns 1 through 13
6 2 2 5 2 10 11 5 -1 0 2 3 11
Column 14
NaN
ans =
6
2
2
5
2
10
11
5
-1
0
2
3
11
NaN
GIBBON www.gibboncode.org
Kevin Mattheus Moerman, [email protected]
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License: https://github.com/gibbonCode/GIBBON/blob/master/LICENSE
GIBBON: The Geometry and Image-based Bioengineering add-On. A toolbox for image segmentation, image-based modeling, meshing, and finite element analysis.
Copyright (C) 2006-2021 Kevin Mattheus Moerman and the GIBBON contributors
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