How to Subset Matrices | Step by Step R Programming Tutorial

Discover how you can subset matrices using R. Join DataCamp today, and start our interactive intro to R programming tutorial for free: https://www.datacamp.com/courses/free-introduction-to-r Just as for vectors, there are situations in which you want to select single elements or entire parts of a matrix to continue your analysis with. Again, you can use square brackets for this, but the fact that you're dealing with two dimensions now, complicates things a bit. Have a look at this matrix containing some random numbers. If you want to select a single element from this matrix, you'll have to specify both the row and the column of the element of interest. Suppose we want to select the number 15, located at the first row and the third column. We type m, open brackets, 1, comma, 3, comma, close brackets. As you can probably tell, the first index refers to the row, the second one refers to the column. Likewise, to select the number 1, at row 3 and column 2, we write the following line: Works like a charm! Notice that the results are single values, so vectors of length 1. Now, what if you want to select an entire row or column from this matrix? You can do this by letting out some of the indices between square brackets. Instead of writing 3, comma, 2 inside square brackets to select the element at row 3 and column 2, you can leave out the 2 and keep the 3, comma part. Now, you select all elements that are in row 3, namely 6, 1, 4 and 2. Notice here that the result is not a matrix anymore! It's also a vector, but this time one that contains more than 1 element. You selected a single row from the matrix so a vector suffices to store this one-dimensional information. To select columns, you can work similarly, but this time the index that comes before the comma should be removed. To select the entire 3rd column, you should write m, open brackets, comma, 3, close brackets. Again, a vector results, this time of length 3, corresponding to the third column of `m`. Now,