Market basket introduction

Market Basket Analysis in R

Christopher Bruffaerts

Statistician

Overview

Market Basket course

Chapter 1: Introduction to market basket analysis
Chapter 2: Metrics and techniques in market basket analysis
Chapter 3: Visualization in market basket analysis
Chapter 4: Case study: Movie recommendations @ movieLens

movie_lens_logo

What is a basket?

Basket = collection of items

Items

Products at the supermarket
Products on online website
DataCamp courses
Movies watched by users

supermarket

Examples of baskets:

Your basket @ the grocery store
Your Amazon shopping cart
Your courses @ DataCamp
The movies you watched on Netflix

Grocery store example

What's in the store?

all_products_emoticons

What are you up for today?

One bread
Three pieces of cheese

bread_3cheese

Grocery store example in R

What's in the store?

store = c("Bread", "Butter",
          "Cheese", "Wine")

set.seed(1234)
n_items = 4
my_basket = data.frame(
                TID = rep(1,n_items),
                Product = sample(
                    store, n_items, 
                    replace = TRUE))

R output

my_basket

  TID Product
1   1   Bread
2   1  Cheese
3   1  Cheese
4   1  Cheese

What's in my basket?

My original basket

One record per item purchased

  TID Product
1   1   Bread
2   1  Cheese
3   1  Cheese
4   1  Cheese

My adjusted basket

One record per distinct item purchased

# A tibble: 2 x 3
    TID Product Quantity
  <dbl> <fct>      <int>
1     1 Bread          1
2     1 Cheese         3

What's in my R basket?

Reshaping the basket data

# Adjusting my basket
my_basket = my_basket %>%
                add_count(Product) %>%
                unique() %>% 
                rename(Quantity = n)

# Number of distinct items
n_distinct(my_basket$Product)

# Total basket size
my_basket %>% summarize(sum(Quantity))

Visualizing items in my basket

Visualizing items in my basket

# Plotting items 
ggplot(my_basket,
    aes(x=reorder(Product, Quantity),
        y = Quantity)) +
          geom_col() +
        coord_flip() +
        xlab("Items") +
        ggtitle("Summary of items
                in my basket")

distribution_basket_bread_cheese

Why are we looking at my basket?

Question: Is there any relationship between items within a basket ?

baskets

Back to examples

Your basket @ the grocery store, e.g. Spaghetti and Tomato sauce
Your Amazon shopping cart, e.g. Phone and a phone case
Your courses @ DataCamp e.g. "Introduction to R" and "Intermediate R"

Happy shopping!

Market Basket Analysis in R