List and arrays

##### Title

##### Question

How to discard alternate numbers from an array and resize the length of an array using R?

R Lists-and-its-Operations 02-03 min 20-30 sec

__Answers:__

Let's say you have an array A as follows -

A<-c(1,2,3,4,5,6)

Suppose you want to keep only the elements at the odd places then you may create a sequence as follows -

seq(1, length(A), 2)

The sequence will start from 1 to the length of array A by skipping one element or taking the alternate element only.

Now to keep only the elements at the odd places then use the following command -

A <- A[seq(1, length(A), 2)]

For even elements start the sequence from '2' instead of '1' as follows -

A <- A[seq(2, length(A), 2)]

We can do its simply by removing those indices. Here is an example,

a=c(1:20)

b=seq(1,length(a),by=2)

a[-b]

Let say array A = 1,2,3,4,5,6,7 and I want to discard the element 1,2,4. How to discard the same and resize the array?

So, here we want to remove indices 1, 2, 4. You may use B= A[-c(1,2,4)] , then B is resized array.

Login to add comment

Login to add comment