Lesson 2 Exercise Questions: Base R syntax, objects, and data types

Let's use some functions.

a. Use sum() to add the numbers from 1 to 10.
Solution
```
sum(1:10)
```
b. Compute the base 10 logarithm of the elements in the following vector and save to an object called logvec: c(1:10).
Solution
```
logvec<- log10(c(1:10))
```
c. What does the function paste() do? Use it to combine the following vectors. Use an _ as a separator.
```
id <- LETTERS[1:5]
idnum<- c(1,3,6,9,12)
```
Solution
```
paste(id,idnum,sep="_")
```
d. What does the function identical() do? Use it to compare the following vectors.
```
a<-seq(2,10,by=2)
b<-c(2,4,6,8,10)
```
Solution
```
#tells us whether the two vectors are the same
identical(a,b)
```

What is the value of each object? You should know the value without printing the value of the object.

mass <- 47.5            # mass?
age  <- 122             # age?
mass <- mass * 2.0      # mass?
age  <- age - 20        # age?
mass_index <- mass/age  # mass_index?

(Question taken from https://carpentries-incubator.github.io/bioc-intro/23-starting-with-r/index.html)

Create the following objects; give each object an appropriate name.

a. Create an object that has the value of the number of bones in the adult human body.

b. Create an object containing the names of four different bones.

c. Create an object with values 1 to 100.
Solution
```
bone_num<- 206
bone_names<- c("talus","calcaneus","tibia","fibula") 
values<-c(1:100) 
```

Vectors include data of a single type, so what happens if we mix different types? Use typeof() to check the data type of the following objects.

num_char <- c(1, 2, 3, "a")
num_logical <- c(1, 2, 3, TRUE, FALSE)
char_logical <- c("a", "b", "c", TRUE)
tricky <- c(1, 2, 3, "4")

Solution

#These were coerced into a single data type
typeof(num_char)
num_char
typeof(num_logical)
num_logical
typeof(char_logical)
char_logical
typeof(tricky)
tricky

(Question taken from https://carpentries-incubator.github.io/bioc-intro/23-starting-with-r/index.html)

Using indexing, create a new vector named combined that contains:

The 2nd and 3rd value of num_char.
The last value of char_logical.
The 1st value of tricky.
Solution
```
combined <- c(num_char[2:3], char_logical[length(char_logical)],
            tricky[1])
```