Create an object (i.e. variable, container) called
testObject and store five numbers in it.
Creating and storing different types of vectors is one of the most essential skills you will need for using R. These first few exercises may seem really trivial, but I promise, you will use these trivial skills so often that you will quickly realize how not trivial they are.
SOLUTION
Okay, so we need an object called testObject. This part
is easy enough. All I have to do is type testObject. The
tricky part is storing something in the object. In this example, we just
need to store five numbers in this object. Let’s go ahead and make our
lives easy by just using the numbers 1 through 5. We can store the
numbers 1 through 5 in an object in a few different ways. Let’s have a
look at those few different ways.
The way a beginner thinks would probably be to save the numbers in the object like so:
testObject = c(1, 2, 3, 4, 5)
This most certainly isn’t wrong, and we achieved our goal. Good, right? Yes, it is! If you did something similar above, that’s great. It means you’ve gotten a grasp on the basics.
But, let’s say we want to be lazy. If I have even ten numbers, typing
the number and comma is a lot of work. I don’t like work. So let’s make
a our lives a little easier by using the fabulous : that R
provides us with to make a sequence of numbers, like so:
testObject = 1:5
Since we are also not stringing numbers together, but using the
sequence operator :, we do not need to concatenate function
c()–you can use it if you want, but you don’t need it.
Everything clear? Hervorragend, then let’s move on to the next exercise.
Create a character vector of your name and save it
as the object Name
HINT: The individual elements of a character vector must be under quotation marks
SOLUTION
I tend to use character vectors quite often (we will hear later in this workshop why), so I find it important to take a little bit of time to get to know them.
If we want a character vector consisting of different individual
elements, then you know what that means: IT’S CONCATINATE TIME! We need
the c() in order to string together different character
elements, like so:
Name = c("Mason", "Allen", "Wirtz")
Of course, if you don’t need individual character elements (but I prefer them and oftentimes you also need the individual elements), you can also solve this without concatenating things.
Name = "Mason Allen Wirtz"
But, using the c() and creating individual character
elements gives us more freedom to play around with the vector. More on
this later.
Create a vector named numbers and save the sequence
1–100 in it.
SOLUTION
I hinted about this above: If we want to have a larger data frame, it
would take us sooooo long to do c(1, 2, 3, 4, 5, 6, …), I personally
would die of boredom. Luckily, we can use the : operator
and let R work its magic and create us a sequence of numbers between 1
and 100, namely like so:
numbers = 1:100
In R, we have arithmetic operators (we will go into logical operators later) with which we can do simple math. Below, you can find a list of these, which are all very self-explanatory.
| Operator | Description |
|---|---|
| + | Addition |
| - | Subtraction |
| * | Multiplication |
| / | Division |
| ^ OR ** | Exponentiation |
Add 1 and 1 together to get two
SOLUTION
I think this one is pretty self-explanatory, but just in case:
1 + 1
[1] 2We can also add vectors together, provided they are numeric. Add the two vectors below together–why does R throw an error?
a = 4:9
b = 10:17
What would we need to do in order to fix this error?
SOLUTION
Only vectors of the same length can meaningfully be added/subtracted
etc. Since vector a contains six values, and vector
b eight values, R added the fist six values together of the
two vectors. Since vector b is longer than vector
a though, the last two numbers in vector b
were added to the first two numbers in vector a.
Basically, vector b realized, “oh no, there are no more
numbers in vector a, what do I do?! Oh, I know, I’ll take
the first two numbers of vector a and add them to my own
last two values!”. R threw us an error to make us aware of this.
Create two vectors (using whatever numerical values you’d like) under
the names a and b (the two variables above
will be overwritten) and divide the two vectors.
SOLUTION
Nothing we haven’t already seen here. We’ll start with generating two vectors, like so:
a = 1:100
b = 101:200
And then let’s go ahead and just divide them by each other. The lovely thing about vectors and being able to save them as objects is that it makes doing simple arithmetic operations like this so easy and readable!
a/b
[1] 0.00990099 0.01960784 0.02912621 0.03846154 0.04761905
[6] 0.05660377 0.06542056 0.07407407 0.08256881 0.09090909
[11] 0.09909910 0.10714286 0.11504425 0.12280702 0.13043478
[16] 0.13793103 0.14529915 0.15254237 0.15966387 0.16666667
[21] 0.17355372 0.18032787 0.18699187 0.19354839 0.20000000
[26] 0.20634921 0.21259843 0.21875000 0.22480620 0.23076923
[31] 0.23664122 0.24242424 0.24812030 0.25373134 0.25925926
[36] 0.26470588 0.27007299 0.27536232 0.28057554 0.28571429
[41] 0.29078014 0.29577465 0.30069930 0.30555556 0.31034483
[46] 0.31506849 0.31972789 0.32432432 0.32885906 0.33333333
[51] 0.33774834 0.34210526 0.34640523 0.35064935 0.35483871
[56] 0.35897436 0.36305732 0.36708861 0.37106918 0.37500000
[61] 0.37888199 0.38271605 0.38650307 0.39024390 0.39393939
[66] 0.39759036 0.40119760 0.40476190 0.40828402 0.41176471
[71] 0.41520468 0.41860465 0.42196532 0.42528736 0.42857143
[76] 0.43181818 0.43502825 0.43820225 0.44134078 0.44444444
[81] 0.44751381 0.45054945 0.45355191 0.45652174 0.45945946
[86] 0.46236559 0.46524064 0.46808511 0.47089947 0.47368421
[91] 0.47643979 0.47916667 0.48186528 0.48453608 0.48717949
[96] 0.48979592 0.49238579 0.49494949 0.49748744 0.50000000What R did here was divide each number in the vector a
by the number in the same position in vector b (i.e. 1/101,
2/102, 3/103 etc.), so we should wind up with a vector of 100 values in
total.
Alright, let’s say we ran an experiment and tested the reaction times of a language learner once a day for seven days. We have the reaction times (these are provided for you, see below), but we want to make a vector with the days of the week.
Create a character vector with the days of the week and save it as
daysOfTheWeek
reactionTimes = rnorm(n = 7, mean = .25, sd = .1) # you don't need to do anything here
daysOfTheWeek =SOLUTION
All we have to do here is string together the days of the week and
save it under the object daysOfTheWeek, only this time we
have a character vector (similar to what we had with our name).
There is also a nice little base R function (we will learn more about
functions later) called weekdays(), which takes a date as
an argument. I put together a few variations of how to generate weekdays
using this function, in case anyone ever really needs to add this to a
data set. Just run the code lines and have a quick look at the
output.
It’s probably important to mention here: There is always an elegant solution to any question, and probably an easier way to do it. While typing the whole vector our like in my solution above is easy, these solutions are also quite elegant and easily readable. Just food for thought.
[1] "Monday" "Tuesday" "Wednesday" "Thursday" "Friday"
[6] "Saturday" "Sunday" [1] "Wednesday" "Thursday" "Friday" "Saturday" "Sunday"
[6] "Monday" "Tuesday" [1] "Monday" "Tuesday" "Wednesday" "Thursday" "Friday"
[6] "Saturday" "Sunday" We could then combine these two vectors to create a data frame using
the function data.frame() from base R (we will learn more
about functions in the next section), like so:
data.frame(daysOfTheWeek, reactionTimes)
daysOfTheWeek reactionTimes
1 Monday 0.2888160
2 Tuesday 0.1972332
3 Wednesday 0.2532501
4 Thursday 0.3731675
5 Friday 0.2436066
6 Saturday 0.3075222
7 Sunday 0.2995326