Filter and Select

Using pipe operator to write one line of code to extract the key information from a data frame

Example: what information can you get regarding Templin as the receiver.location on the latest date

library(tidyverse)

#transport_data <- read_csv("data/transport-data.csv")

transport_data %>% 
  select(sender.location,receiver.location) %>% 
  unique() # unique sender and receiver locations

# it looks like a city called Templin is a popular receiver location. Let's filter this location
transport_data %>% 
  filter(receiver.location=="DEU, Templin")

# what is the most recent date for Templin
transport_data %>% 
  select(date) %>% 
  .[[1]] %>% 
  max() # this code shows that the condition of max date exists

[1] "1989-08-23"

# add this condition to the filter
transport_data %>% 
  filter(receiver.location=="DEU, Templin" & date == max(date)) # return zero rows

# this is because the condition of the max date is set to all the data not just the data for Templin. 
#to solve the problem, we need to have multiple fiters applied
transport_data %>%
  filter(receiver.location== "DEU, Templin") %>%
  filter(date == max(date))

select statement

Apart from select the column names, what else can you do with select statements?

# select statement
# select columns with word "receive" in it
transport_data %>%
  filter(receiver.location== "DEU, Templin") %>%
  filter(date == max(date)) %>% 
  select(contains("receive"))

# select continuous column names
transport_data %>%
  filter(receiver.location== "DEU, Templin") %>%
  filter(date == max(date)) %>% 
  select(sender.location:receiver.longitude)

# rearrange the order of the columns. If you have many columns, and you want one column to be the first column, and then use everything().
transport_data %>%
  filter(receiver.location== "DEU, Templin") %>%
  filter(date == max(date)) %>% 
  select(number.of.items,everything())