finding minimum number in each matrix row

Question

I am attempting to write a code to find a minimum number from the 'distance' matrix, excluding zeroes from the matrix.

distance=[0    0.44    0.40    0.63    0.89
0.44    0       0.44    0.72    1.00
0.40    0.44    0       0.28    0.56
0.63    0.72    0.28    0       0.28
0.89    1.00    0.56    0.28    0]

for  i=1:Nodes
    for  j=1:Nodes
        if (distance(i,j)~=0)

        [mini(i,:)]=[min(distance(i,:))];
        end
    end
end

Any help is appreciated! Thank you!

What results does the code that you have give you?

John
– John

2013-07-15 22:19:00 +00:00
Commented Jul 15, 2013 at 22:19 — John
– John, Commented Jul 15, 2013 at 22:19
it gives me an array of zeros :(

happyme
– happyme

2013-07-15 22:20:08 +00:00
Commented Jul 15, 2013 at 22:20 — happyme
– happyme, Commented Jul 15, 2013 at 22:20
use dinstead of distance.

collapsar
– collapsar

2013-07-15 22:20:37 +00:00
Commented Jul 15, 2013 at 22:20 — collapsar
– collapsar, Commented Jul 15, 2013 at 22:20
that ain't the issue, sir!!

happyme
– happyme

2013-07-15 22:22:10 +00:00
Commented Jul 15, 2013 at 22:22 — happyme
– happyme, Commented Jul 15, 2013 at 22:22

ypnos · Accepted Answer · 2013-07-15 22:21:20Z

5

The correct answer is:

d = distance;
d(~d) = inf;
mini = min(d);

First you get rid of the zero entries, then you let Matlab calculate the minimum per row.

You should always try to avoid loops in Matlab.

answered Jul 15, 2013 at 22:21

ypnos

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2 Comments

happyme Over a year ago

Thank you so much! I will try and avoid loops in my further programs!

Dennis Jaheruddin Over a year ago

Very nice, this definately answers the question as it was asked. However @happyme as it is a distance matrix, you usually may be more interested in this instead: d(logical(eye(size(d)))) = Inf This enables you to calculate the minimum distance to 'other' points. (Same result for your example matrix)

Dennis Jaheruddin · Accepted Answer · 2013-07-16 09:06:01Z

0

Though I would recommend a vectorized solution as @ypnos offered, here is one way to make your loop work.

mini = inf(1,Nodes)
for  i=1:Nodes
    for  j=1:Nodes
        if (distance(i,j)~=0) %Consider using if i~=j if you want the distance to 'other' points
            mini(j)=min(distance(i,j),mini(j));
        end
    end
end

answered Jul 16, 2013 at 9:06

Dennis Jaheruddin

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