Introduction to Find Function Matlab
MATLAB provides its user with a basket of functions, in this article we will understand a powerful function called ‘Find’. In its simplest form, find function will return the indices of array X that points to the nonzero elements. If it finds none, the function will return an empty matrix.
Syntax of Find Function:
R = find(X)R = find (X, n)R = find (X, n,direction)[row, col] = find ()[row, col, v] = find ()
Description of Find in Matlab
Below will learn all the Find function in Matlab one by one accordingly:
1. R = find(A)
- Here A is an array, this function will return a vector that will contain linear indices of each non zero elements of A.
- Let’s assume A to be a vector then R will return a vector which will have the same orientation as x.
- If A is to be a multidimensional array, R will give back a column vector containing linear indices.
- If A has all zeros or empty values, then R will give us an empty array.
Let us now understand this concept with an example:
Here, X is a 3 x 3 matrix:
Code:
X = [2 1 1; 0 3 1; 0 0 1]
k = find(X)
Below is how the console will look like:
Output:
Let us use a logical operator ~ to locate the zero values.
Code:
X = [2 1 1; 0 3 1; 0 0 1]
R1 = find(~X)\
Output:
2. R = find (X, n)
This function will return the first n indices for the non zero values in X. Below is an example to understand this find function:
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X is a 3 x 3 matrix:
Code:
X=[8 1 6;3 5 7;4 9 2]
k = find(X < 10, 5)
Output:
3. R = find (X, n,direction)
This function will return the n indices for non zero elements in either last or first direction as specified in the function. Below is an example to understand this find function:
Code:
X is a 3 x 3 matrix:
X=[0 1 0;3 0 7;0 9 0]
k = find (X, 3, last)
Output:
4. [row, col] = find()
This function will return the row and column subscripts of non zero elements of array X for any of the above-mentioned functions. Below is an example to understand this find function:
Code:
X is a 3 x 3 matrix:
X=[1 3 1;8 0 1;5 4 6]
[row, col] = find(X>0 & X<5, 3)
Output:
![[row, col] = find()](https://cdn.educba.com/academy/wp-content/uploads/2020/01/Find-Function-Matlab-4.png)
5 . [row, col, v] = find()
This function will return vector ‘v’ in addition to the row and column subscripts of non zero elements of array X for any of the above-mentioned functions. Below is an example to understand this find function:
Code:
X is a 3 x 3 matrix:
X=[1 3 0;8 0 1;0 4 0]
[row, col, v] = find(X)
Output:
Conclusion
We can find elements of arrays that satisfy a defined condition. For achieving this, we need to use find function along with a relational expression. So, find(A<4) will return linear indices of the elements of A which are less than 4. We can also directly find elements in A that fulfill the given condition like A<5. For this, we simply use A(A<5). Here we can avoid making calls to function like A(find(A<5)) When we execute find function with any relational operation like A>1, we must remember that here, the result will be a matrix of 1s & 0s. Example: [row, col, A] = find(A>1) will return column vector with logical true values.
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