Vectors in the R Language are the simplest data structures. A vector in R is also an object containing elements of the same data type. To create a vector (say ‘x’) of the same type (that is data type is double) of elements consisting of five elements one can use the c() function. For example,
Creating Vectors in R using the c() Function
x <- c(10, 7, 3, 2, 1)
The c() function can be used to combine a different number of vectors into a single vector. A single number is regarded as a vector of length one. For example, a vector (say ‘y’) is created by combining the existing vector(s) with a single number.
Appending a Number to an Existing Vector(s)
One can append a number to an existing vector or even append a vector with another vector. For example, vectors in R Language can be appended like:
y <- c(x, .55) z <- c(x, y)
Extracting Vector Element(s)
The simplest example to select a particular element of a vector can be performed by using a subscription mechanism. That is, use the name of the vector with a square ([ ]) bracket with a number in it indicating the position of a vector element. For example,
# shows first element of vector x > x[1:2] # shows first two elements of vector 'x' > x[3:5] # shows elements of vector 'x' from index 3 to 5
Note that a positive number is used as a subscript index in a square bracket. A positive subscript indicates the index (position) of a number to extract from the vector. A negative number as the index can also be used, which is used to select all the elements except the number(s) that are used in the square bracket ([ ]).
An example of a negative index is;
x[-1] # shows all elements of vector 'x' except first element x[-(1:2)] # shows elements of vector 'x' except first two elements
Also note that if the subscripting number exceeds the number of elements in a vector, then it will result in NA (not available). For example,
x[7] x[1:10]
Updating Vector Elements
One or more elements of a vector can be changed by the subscripting mechanism. For example, to change the 4th element of a vector, one can proceed as follows;
x[4] <- 15 # 4th position of vector 'x' is updated to 15 x[1:3] <- 4 # first three numbers are updated to 4 x[1:3] <- c(1,2,3) # first three numbers are updated to 1, 2, and 3
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