# R | Slicing and Extracting Data

### Indexing Vectors

• x[n] nth element
• x[-n] all but the nth element
• x[1:n] first n elements
• x[-(1:n)] elements from n+1 to the end
• x[c(1,4,2)] specific elements
• x[“name”] element named “name”
• x[x > 3] all elements greater than 3
• x[x > 3 & x < 5] all elements between 3 and 5
• x[x %in% c(“a”,”and”,”the”)] elements in the given set

### Indexing Lists

• x[n] list with elements n
• x[[n]] nth element of the list
• x[[“name”]] element of the list named “name”
• xname id
| | Category: R

# R Objects: Data Types

• ##### OBJECTS
• R has five basic classes of objects:
1. Character
2. Numeric
3. Integer
4. Complex
5. Logical

However, the most basic object is a vector.

• There are two things which you should remember when dealing with vectors.
1. A vector can only contain objects of the same class.
2. AND there is an exception to this, a list. A list looks like a vector, but can have different classes.

To create an empty vector use the following function:

 `vector()`
Vectors can be created by using the following:
 ```c() # used to concatenate individual values together : # to create a sequence, such as 1:10 seq() # to create more complex sequences rep() # replicates values sort() # ordering elements in a vector order() # ordering elements in a vector```

An example of using rep()

 ```rep(5,2) #a vector of two fives [1] 5 5```

An example of using c()

 ```c(3,2,1) # vector of three numeric elements in that order [1] 3 2 1```

An example of using seq()

 ```seq(4,20, by = 2) [1] 4 6 8 10 12 14 16 18 20 seq(1,length = 20, by =4) [1] 1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77```
| | Category: R