Challenge 9

Creating a function

library(tidyverse)
library(ggplot2)
library(lubridate)

knitr::opts_chunk$set(echo = TRUE, warning=FALSE, message=FALSE)

Read in data

set.seed(42)
poul <- read_csv('_data/poultry_tidy.csv')
head(poul)

# A tibble: 6 × 4
  Product  Year Month    Price_Dollar
  <chr>   <dbl> <chr>           <dbl>
1 Whole    2013 January          2.38
2 Whole    2013 February         2.38
3 Whole    2013 March            2.38
4 Whole    2013 April            2.38
5 Whole    2013 May              2.38
6 Whole    2013 June             2.38

Create Functions

Create date from year and month:

add_date <- function(data) {
    data <- mutate(data, Month_num = recode(Month, "January" = 1, "February" = 2, "March" = 3, "April" = 4, "May" = 5, "June" = 6, "July" = 7, "August" = 8, "September" = 9, "October" = 10, "November" = 11, "December" = 12))
    data <- mutate(data, Date=make_date(Year, Month_num))
    return(data)
}

add_date(poul)

# A tibble: 600 × 6
   Product  Year Month     Price_Dollar Month_num Date      
   <chr>   <dbl> <chr>            <dbl>     <dbl> <date>    
 1 Whole    2013 January           2.38         1 2013-01-01
 2 Whole    2013 February          2.38         2 2013-02-01
 3 Whole    2013 March             2.38         3 2013-03-01
 4 Whole    2013 April             2.38         4 2013-04-01
 5 Whole    2013 May               2.38         5 2013-05-01
 6 Whole    2013 June              2.38         6 2013-06-01
 7 Whole    2013 July              2.38         7 2013-07-01
 8 Whole    2013 August            2.38         8 2013-08-01
 9 Whole    2013 September         2.38         9 2013-09-01
10 Whole    2013 October           2.38        10 2013-10-01
# … with 590 more rows

Plot a trend line given a product name:

plot_trend <- function(data, product) {
    data <- filter(data, Product == product)
    ggplot(data, aes(x = Date, y = Price_Dollar)) +
        geom_line() +
        ggtitle(paste('Price of Poultry (', product, ')'))
}

plot_trend(add_date(poul), 'Thighs')

plot_trend(add_date(poul), 'Whole')