Dates and Time + Tables

Question 1

Dates and Time Data

Answer 1

• Have traits of both character and numeric data.

Question 2

as.Date()

Answer 2

• Function that converts character representations of dates (without times).
• Best used with dates that appear without times.
• Can allow for a variety of input formats using the format = argument.

Question 3

strptime()

Answer 3

• Function that converts character representations of dates and times to Unix (POSIX).
• Used when data has times, time zones, AM/PM time stamps, etc.

Question 4

Lubridate

Answer 4

• Package that makes character representations of dates / times easy to convert.
• Handles the computation of intervals easily.

Question 5

Beginning Data in R

Answer 5

• Almost all dates are stored by R as the number of days or seconds from January 1, 1970.

Question 6

unclass(argument)

Answer 6

• Function in R that can be used to reveal R’s storage of the date.

Question 7

Formatting of Dates in R

Answer 7

• R expects the format of YYYY-MM-DD or YYYY/MM/DD.

Question 8

Format Options for as.Date()

Answer 8

1) %B: full month spelled out.
2) %b: abbreviated month spelled out
2) %d: day 1-31.
3) %y: 2 digit year.
4) %Y: 4 digit year.
4) %h: hour in 24 hours.
5) %S: seconds.
6) %I: 12 hour clock.
7) %M: minutes.
8) %p: AM/PM.

Question 9

weekdays(), months(), quarters()

Answer 9

• Base R functions that can be used.

- Return character vectors.

Question 10

hours(), minutes()

Answer 10

• Functions in lubridate which can be useful for variables with time stamps.

Question 11

table(vector_argument)

Answer 11

• Function that create the simplest table.
• Generates a one-way table.
• Can utilize the option levels = to name the columns.
• For example,
  offcampus$RDOW

Question 12

table(argument1,argument2)

Answer 12

• Function that creates a simple two way table.
• argument1 is for the row variable.
• argument2 is for the column variable.

Question 13

prop.table(argument)

Answer 13

• Function that tells R to display proportions for tables.
• Argument requires a table to serve as data.
• All the number sin the table will cum to one.