Summing Rows in Matlab

Introduction

In Matlab, you may come across a situation where you need to sum the values of rows of a matrix. For example, you might have a matrix where each row represents a different experiment, and you want to find the total value of all experiments. This can be easily achieved using the built-in sum function in Matlab.

Syntax

The syntax for the sum function in Matlab is as follows:

B = sum(A,dim)

where:

• A is the input matrix.
• dim is the dimension along which the summation is performed. By default, dim is set to 1, which means the summation is performed along the first dimension (i.e. the rows).
• B is the output matrix with the sum of each row (or column).

Examples

Example 1: Summing Rows of a Matrix

Suppose we have a matrix A with 3 rows and 4 columns:

A = [1 2 3 4; 5 6 7 8; 9 10 11 12];

To find the sum of each row, we can simply call the sum function with dim=2:

B = sum(A,2);

The output B is a column vector with the sum of each row:

B = 
    10
    26
    42

Example 2: Summing Columns of a Matrix

If we want to find the sum of each column instead, we can simply call the sum function with dim=1:

B = sum(A,1);

The output B is a row vector with the sum of each column:

B = 
    15    18    21    24

Conclusion

The sum function in Matlab is a powerful tool for summing the values of rows (or columns) of a matrix. It can be easily implemented with just a few lines of code, and can save you a lot of time and effort when working with matrices.