Returning Incorrect index of array
6 views (last 30 days)
Show older comments
Khairul Nur
on 9 Jul 2021
Commented: Khairul Nur
on 22 Jul 2021
hi,
The simple code below try to find the min value and its index, excluding 0
x = [0 0.5 4 5];
[r,index] = min(x(x>0))
The min value is correctly founded as 0.5. However, why the index returns as 1, it suppose to return 2
r =
0.5000
index =
1
Please help to solve. TQVM
2 Comments
Stephen23
on 12 Jul 2021
Without changing any data values:
x = [0,0.5,4,5];
idx = find(x);
[val,idy] = min(x(idx));
val
idx(idy)
Accepted Answer
Bjorn Gustavsson
on 9 Jul 2021
It returns 1 for the index because the way you call min, x(x>0) becomes the array [0.5 4 5], and the first element of that array is the smallest.
HTH
3 Comments
Scott MacKenzie
on 9 Jul 2021
I'm not sure if there's a one-liner, but this will work:
x = [0 0.5 4 5];
x(x==0) = realmax;
[~, idx] = min(x)
More Answers (1)
Viranch Patel
on 9 Jul 2021
So if you write y = x(x>0), then it will take value only which is greater than 0 from the x and put it into y.
x = [0 0.5 4 5];
y = x(x>0);
[r,index] = min(x(x>0));
So y will be equal to [0.5000 4.0000 5.0000].
Now if you find minimum then the index will be 1 not 2.
I hope you get the answer:)
3 Comments
Viranch Patel
on 9 Jul 2021
If I'm guessing correct, you want to get the index of the lowest positive value. Then you can do this using a single for loop in which you can have two variables, one will store the minimum value and one will store the index.
index = 0;
x = [0 0.5 4 5];
min_value = max(x);
len = length(x);
for i = 1:len
if x(i) < min_value && x(i) > 0
min_value = x(i);
index = i;
end
end
This is quite straight-forward. So you can edit this according to your need.
See Also
Categories
Find more on Matrix Indexing in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!