Is Member Matlab

How To Articles

As a longtime user of MATLAB, I can confidently say that the ismember function is an invaluable tool in my coding arsenal. Whether you’re a newbie or a seasoned programmer, understanding how ismember works and harnessing its power can greatly improve your MATLAB programming skills.

What is ismember?

In MATLAB, ismember is a logical function that allows you to check whether elements from one array are present in another array. It returns a logical array with the same size as the first input array, with elements set to true if they are found in the second input array, and false otherwise.

Let’s dive into the syntax of ismember:

[Lia, Locb] = ismember(A, B);

  • A: This is the first input array, where we want to check if its elements are present in B.
  • B: This is the second input array, where we are searching for the elements from A.
  • Lia: This is the logical output array, indicating the presence or absence of elements from A in B.
  • Locb: This is an optional output array that contains the index values of the elements from A that are found in B. It can be useful when you need to know the index locations of the matching elements.

It’s important to note that the elements in both A and B must be unique, as ismember uses element-wise comparison to determine the matches.

Applications of ismember

The ismember function is incredibly versatile and can be used in various scenarios. Here are a few examples:

1. Removing Duplicates

One common use case of ismember is to remove duplicate elements from an array. By passing the array to both A and B inputs of ismember, you can easily identify and eliminate the duplicates.

A = [1, 2, 3, 4, 4, 5, 6];
unique_elements = A(~ismember(A, A(1:end-1)));

This code snippet removes the duplicates from array A and stores the unique elements in the unique_elements variable.

2. Subset Validation

Another useful application of ismember is validating whether one array is a subset of another. By comparing the logical output with the original array, you can easily check if all elements in one array exist in another.

A = [1, 2, 3];
B = [1, 2, 3, 4, 5, 6];
is_subset = all(ismember(A, B));

In this example, is_subset will be true because all elements of A are present in B.


ismember is a versatile function in MATLAB that allows you to efficiently check for the presence of elements from one array in another. Its applications range from removing duplicates to subset validation, making it an essential tool for any MATLAB programmer’s toolkit. By mastering the usage of ismember, you can greatly enhance your programming capabilities and streamline your code.