  Course Content

# R Introduction: Part II

R Introduction: Part II

##   matrix() Function

Sometimes you may have only one vector that you need to convert into a matrix. How can it be done? The answer is simple - by using the `matrix()` function.

This function has the following parameters:

These are not all the parameters, but the most important for us.

• `data` - is the vector that we want to use to build the matrix.
• `nrow` - number of rows in a new matrix.
• `ncol` - number of columns in a new matrix.
• `byrow` - logical, should the matrix be filled by rows. It's important to note that the length of the vector filled as the `data` parameter must be divisible by `nrow` or `ncol`. If both parameters are set, then `nrow*ncol` must equal the vector length. For example, let's construct a 3x3 matrix with integers from 1 to 9.  As you can see, this matrix was built from above to below first. Let's set parameter `byrow` to `T` and compare the results.  As you can see, we filled this matrix from left to right. We were free to leave only one of the `nrow` or `ncol` parameters since 9 (number of elements in the vector) is divisible by 3 and returns an integer result.

Given a vector of numbers named `num`.
Use only the `matrix()` function, and think about the correct values of parameters.
How does `seq()` function work? `seq(a, b)` generates integers from `a` to `b` inclusive. `seq(a, b, c)` generates integers from `a` to `b` with the step `c`. 