In MATLAB, the arrays are used to represent the information and data. You can use indexing to access the elements of the array. In MATLAB the array indexing starts from 1. To find the index of the element in the array, you can use the find() function. Using the find() function you can find the indices and the element from the array. The find() function returns a vector containing the data.
Syntax:
- find(X) : Return a vector containing the indices of elements
- find(X,n): Return first n indices of the elements in X
- find(X,n, Direction): find n indices in X according to the Direction where Direction – ‘first‘ or ‘last‘
- [row,col] = find(): It returns the row and column subscript of element in array
- [row,col,V] = find(): returns vector V containing non-zero elements
Now let’s see how to find an index of any element in an array using the find() function with the help of examples.
find(x)
find(X) returns a vector containing the linear indices of each nonzero element in array X.
Example 1:
Matlab
array = [1 2 3 4 5 6]
index = find(array==3)
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Output:
Note: If the array contains duplicates then find(X) function will return all the indices of that integer.
Example 2:
Matlab
array = [1 2 3 4 5 6 2 4 2]
index = find(array==2)
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Output:
When the array contains duplicate values the find() function will print all the indices of that corresponding element. So if you don’t want all the indices of that element you can use the find(X,n) function.
find(X,n)
Return first n indices of the elements in X.
Example:
Matlab
array = [1 2 3 4 5 6 2 4 2]
index = find(array==2,1)
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Output:
find(X,n,Direction)
You can also find the index of the elements from both directions in the array. Both directions mean from starting and from last by using find(X,n,Direction). This function find n indices in X according to the Direction. The Direction parameter accepts either ‘first’ or ‘last’. If the direction is first it will return first n indices of that corresponding element or if the direction is last it will return the indices by traversing from the end of the array. By default, the Direction parameter is ‘first’.
Example 1:
Matlab
array = [1 2 3 4 5 6 2 4 2]
index = find(array==2,2,'first')
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Output:
Example 2:
Matlab
array = [1 2 3 4 5 6 2 4 2]
index = find(array==2,2,'last')
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Output:
[row,col] = find(x)
For finding the index of an element in a 3-Dimensional array you can use the syntax [row,col] = find(x) this will give you the row and the column in which the element is present.
Example:
Matlab
array = [1 2 3; 4 5 6; 7 8 9]
[row,col] = find(array==5)
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Output:
[row,col,v] = find(X)
If you want to find the indices of all the non-zero elements present in the 3-dimensional array you can use [row,col,v] = find(X) where X is our array. This will find all indices of all non-zero elements present in the array and store them into the vector v.
Example:
Matlab
x = [1 9 0; 3 -1 0; 0 0 7]
[row,col,v] = find(x)
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Output:
