Progress Log 105 (R): Create and Name Vectors

I’m taking an edX course entitled “Introduction to R for Data Science” and all of the concepts described below come from that course.

Vectors

  • A sequence of data elements.
  • Same basic data type.
    • You can have character vectors, numeric vectors, logical vectors, etc.

Create a Vector c()

Character Vector

Suppose you are playing a card game and record the suit of 5 cards you draw from a deck. A possible outcome and corresponding vector to contain this information could be like the one below.

We can also assign this character vector to a new variable. Here we will assign it to drawn_suits.

We can assert that it is a vector by typing is.vector().

Integer Vector

Suppose you want to store how many cards of each suit remain after you drew the five cards. Let’s call this vector remain. There are 11 more spades, 12 more hearts, 11 diamonds, and all 13 clubs remain.

If you print remain in the console, it looks okay, but it’s not very informative. How does somebody else know that the first value corresponds to spades?

Naming the vector

In R, you can use the names() function to name the vector.

Method 1

  1. Let’s create another character vector, suits, that contains the strings “spades”, “hearts”, “diamonds”, and “clubs” – the names you want to give your vector elements.
    1. suits <- c("spades", "hearts", "diamonds", "clubs")
  2. Set the names of the elements of remain to the string in suits
    1. names(remain) <- suits
  3. Print remain in the console to make sure that the suits information is accompanied by the proper labels.

Method 2

If you don’t want to bother setting the names after creating the vector you can do as follows:

As you can see, it is not necessary to surround the names “spade”, “hearts”, “diamonds”, and “clubs” in this example with double quotes, although it works fine.

Single value = vector

R does not provide a data structure to hold a single number or a single character string or any other basic data type: they’re all just vectors of length 1.

Examples:

You can check whether my_apples and my_oranges are vectors by using the is.vector() function.

You can check the length of vectors by using the length() function.

Vectors are homogeneous

  • Can only hold elements of the same type.
  • Often called atomic vectors to differentiate them from lists (which can hold elements of different types).
  • Automatic Coercion occurs if you try to build a vector that contains different data types. R will automatically coerce your vector so they then have the same data type.

Coercion for vectors

Suppose now you are recording the ranks of the cards. You might want to combine the result of drawing 8 cards like this, creating a vector drawn_ranks.

If you now inspect this vector, you will see that the numeric vector elements have been coerced to characters, to end up with a homogeneous character vector.

Practice

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