r data structures
# R’s base data structures can be organised by their dimensionality
# (1D, 2D, or ND) and whether they’re homogeneous (all contents must be
# of the same type) or heterogeneous (the contents can be of different
# types). This gives rise to the five data types most often used in data
# analysis:
Dimension Homogeneous Heterogeneous
1D Atomic vector List
2D Matrix Data frame
ND Array
# Note, atomic vectors are always flat (i.e. they can't be nested), they
# are usually of type logical, integer, double (often called
# numeric), or character, and other R objects are built on atomic
# vectors.
# Note, because atomic vectors cannot contain mixed types, if you
# combine types, they will be coerced to the most flexible type of
# the types you used. In order of increasing flexibility, the types
# are: logical -> integer -> double -> character