• One dimensional types (‘vectors’):
  • Character: strings or individual characters, quoted
  • Numeric: any real number(s)
  • Integer: any integer(s)/whole numbers
  • Factor: categorical/qualitative variables
  • Logical: variables composed of TRUE or FALSE
  • Date/POSIXct: represents calendar dates and times

• seq(from, to, by = ) can create sequences

seq(from = 1, to = 5) 

## [1] 1 2 3 4 5

seq(from = 1, to = 5, by = 0.1) 

##  [1] 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8
## [20] 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7
## [39] 4.8 4.9 5.0

logical is a type that only has two possible elements: TRUE and FALSE

x = c(TRUE, FALSE, TRUE, TRUE, FALSE)
class(x)

## [1] "logical"

z = c("TRUE", "FALSE", "TRUE", "FALSE")
class(z)

## [1] "character"

as.logical(z)

## [1]  TRUE FALSE  TRUE FALSE

• as.numeric, as.character, as.logical, as.integer - “coerces”/changes a vector into that data type - MAY RESULT in NA
• is.numeric, is.character, is.logical, is.integer gives a single TRUE or FALSE if that vector is that class

is.logical(c(TRUE, FALSE))

## [1] TRUE

is.numeric(c(TRUE, FALSE))

## [1] FALSE

as.numeric(c(TRUE, FALSE))

## [1] 1 0

as.numeric(c("5", "0", "$0 "))

## Warning: NAs introduced by coercion

## [1]  5  0 NA

as.character(c(TRUE, FALSE))

## [1] "TRUE"  "FALSE"

as.integer(c(TRUE, FALSE))

## [1] 1 0

as.logical(c(5, 0))

## [1]  TRUE FALSE

A factor is a special character vector where the elements have pre-defined groups or ‘levels’. You can think of these as qualitative or categorical variables:

x = factor(c("boy", "girl", "girl", "boy", "girl"))
x 

## [1] boy  girl girl boy  girl
## Levels: boy girl

class(x)

## [1] "factor"

Note that levels are, by default, in alphanumerical order.

• don’t use as.factor, use factor, even when re-creating a factor
• don’t use the relevel function. Use the levels function to grab the levels if you need.
  
• The fct_relevel function in forcats (in tidyverse) is fine to use.
• Check out the forcats functions fct_inorder, fct_infreq, fct_lump

• Use the lubridate package - period.
• Change dates using ymd, dmy, or mdy or other combinations.
  • lubridate cannot guess this - you also don’t want it to
  • If some are ymd and others are dmy, you need to clean
  • as_date also is a good function to try
• Make datetimes using ymd_hms, ymd_hm, or ymd_h
  • as_datetime also is a good function to try

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