Lecture 7
R Basics
September 17, 2024
R Basics
R Basics
Accessing Subsets of Vectors in R
- An important aspect of working with R objects is knowing how to “index” them.
- Indexing enables the filtering of data subsets for further analysis.
- We focus on two primary types of vector indexing: positional and logical.
- To access elements in a vector
vec, usevec[]with one of these methods:- Single index:
vec[n]wherenis a positive integer - Vector of indices:
vec[c(i, j, k)]wherei,j,kare positive integers - Logical condition:
vec[condition]where condition is a logical expression
- Single index:
R Basics
Accessing Subsets of Vectors in R
Positional Indexing
- An index is a positional reference (e.g., 1, 2, 3) used to access individual elements within data structures like a vector.
- In R, the index is positive integer, starting at 1.
R Basics
Accessing Subsets of Vectors in R
A Vector of Indices
- Selecting multiple elements by providing a vector of indices
R Basics
Accessing Subsets of Vectors in R
Logical Indexing
- Using conditions to filter elements of a vector.
R Basics
Tidy data.frame: Variables, Observations, and Values
There are three rules which make a
data.frametidy:- Each variable must have its own column.
- Each observation must have its own row.
- Each value must have its own cell.
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Lecture 7 R Basics Byeong-Hak Choe bchoe@geneseo.edu SUNY Geneseo September 17, 2024