Week 3 - Data wrangling

Question 1

Name the variable types

Answer 1

int
db
num
chr
logi
factor
date/dttm
I don't need charizard. Link for days.

Question 2

What does filter do?

filter(var %in% c(“PRCP”, “TMAX”, “TMIN”))

Answer 2

It takes the column named var, and only shows rows where prcp tmax and tmin occur.

Question 3

How do I order a table by a certain column?

Answer 3

use the arrange function.

Question 4

How to choose only certain variables?

Answer 4

Use select. E.g.
airport %>%
select(AIRPORT, LATITUDE, LONGITUDE, AIRPORT_IS_LATEST, DISPLAY_AIRPORT_NAME)

Question 5

What does mutate do?

Answer 5

Allows you to create new, or transform existing variables.

Question 6

What do these do:
%/%
%%

Answer 6

%/% Integer division

%% Remainder (mod)

Question 7

What function to use to calculate quantities on a column?

Answer 7

Summarise

mean, median, sd, min max etc.

Question 8

How to group and ungroup data?

Answer 8

Using group_by()
  group_by(word) %>%
  summarise(m = mean(value), s = sd(value), 
            mx = max(value), mn = min(value))

using ungroup()

Question 9

What are the types of joins?

Answer 9

Left / right join

Inner / outer