Create and Name Matrices | Simple R Programming Tutorial
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Data Literacy50%
Key Takeaways
Create and name matrices in R using the matrix function, specifying dimensions such as nrow or ncol, and filling values column-wise or row-wise using the byrow argument.
Original Description
Understand how to create and name your matrices in R.
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So, what is a matrix. Well, a matrix is kind of like the big brother of the vector. Where a vector is a _sequence_ of data elements, which is one-dimensional, a matrix is a similar collection of data elements, but this time arranged into a fixed number of rows and columns. Since you are only working with rows and columns, a matrix is called two-dimensional. As with the vector, the matrix can contain only one atomic vector type. This means that you can't have logicals and numerics in a matrix for example. There's really not much more theory about matrices than this: it's really a natural extension of the vector, going from one to two dimensions. Of course, this has its implications for manipulating and subsetting matrices, but let's start with simply creating and naming them.
To build a matrix, you use the matrix function. Most importantly, it needs a vector, containing the values you want to place in the matrix, and at least one matrix dimension. You can choose to specify the number of rows or the number of columns. Have a look at the following example, that creates a 2-by-3 matrix containing the values 1 to 6, by specifying the vector and setting the nrow argument to 2:
R sees that the input vector has length 6 and that there have to be two rows. It then infers that you'll probably want 3 columns, such that the number of matrix elements matches the number of input vector elements. You could just as well specify ncol instead of nrow; in this case, R infers the number of _rows_ automatically.
In both these examples, R takes the vector containing the values 1 to 6, and fills it up, column by column. If you prefer to fill up the matrix in a row-wise fashion, such that the 1, 2 and 3 are in the first row, you can set the `byrow` argument of matrix to `TRUE`
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