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# Find

Asked by AP on 6 Jul 2011

I have a matrix 10000×2, named A. The first column is x and the second column is y. I am trying to find the number of element where the following condition holds:

```y<x+b && y>x-b
```

where b is a constant. I used FIND command to achieve this. I want to make sure it is correct. Thank you very much.

```numel(find((A(:,2)<A(:,1)+b) & (A(:,2)>A(:,1)-b)))
```

I would appreciate quick responses :))))))

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Answer by Matt Fig on 6 Jul 2011

Use & instead of && when dealing with array comparisons.

Also, this is faster:

```sum((A(:,2)<A(:,1)+b) && (A(:,2)>A(:,1)-b))
```

## 1 Comment

AP on 6 Jul 2011

that was soooo quick thanks.

Answer by Paulo Silva on 6 Jul 2011
```a=randi([1 10],10,2); %make up some data
x=a(:,1);
y=a(:,2);
b=5;
sum(y<x+b & y>x-b)
```