Day2.md

R Fundamentals - Day 2

Day1	Day2	Day3	Day4

• R Session for Day 2

Questions & Review

• attach() - NOT UNDER ANY CIRCUMSTANCES (unless never change)

Data Types/Structures

1. [Basic data types - vectors]

   • Hierarchy of data types and implicit coercion
   • Class, typeof, length
   • dim, names
   • Sequences
   • NAs and is.na()

2. Vectorized/Element-wise Functions & the Recycling Rule

   • The family of apply functions.

3. Subsetting rules

   1. index/position – x[ c(10, 2) ]
      1. Subset with 0
   2. logical indexing – x[ c(FALSE, FALSE, TRUE, TRUE, FALSE) ]
   3. name – x[ c("a", "xyz") ]
   4. exclusion via negative position/index – x[ - c(1, 3, 9) ]
   5. empty – x[]
   6. Subsetting outside the length of a vector
   7. drop = TRUE/FALSE - factors and
   8. 2-dimensional subsetting
   9. by two column matrix
   10. by matrix

4. Categorical data - factors

5. Lists

6. Making Lists - c() and list()

7. Subsetting Lists -[, [[, $

   1. [ verus [[
   2. partial name matching with $ and not with [[
   3. hierarchical indexing

8. Data Frames

9. Subsetting in 2-Dimensions

10. Matrices

    • Subsetting a matrix by matrix

11. Attributes Generally