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The Kaggle What's Cooking challenge

Sat, 09 Jan 2016

Machine Learning Kaggle

In this blog post, we'll have a look at the Kaggle What's Cooking data challenge.

This competition is all about predicting which country a recipe is from, given a list of its ingredient. For example, assume you have a recipe that reads:

plain flour, ground pepper, salt, tomatoes, ground black pepper, thyme, eggs, green tomatoes, yellow corn meal, milk, vegetable oil

Can you guess from which cuisine this is? As this recipe comes from the training set of this challenge, I can tell you that the expected answer is Southern US.

Without further ado, let's dive in. First, let us have a look at the training data.

Exploring the training data

We'll use pandas to go through the data. First, let's read the json file containing the recipes and the cuisines:

import pandas as pd

df_train = pd.read_json('train.json')

Let's look at the head of the data:

df_train.head()

	cuisine	id	ingredients
0	greek	10259	[romaine lettuce, black olives, grape tomatoes...
1	southern_us	25693	[plain flour, ground pepper, salt, tomatoes, g...
2	filipino	20130	[eggs, pepper, salt, mayonaise, cooking oil, g...
3	indian	22213	[water, vegetable oil, wheat, salt]
4	indian	13162	[black pepper, shallots, cornflour, cayenne pe...

We can see the structure of the data: a cuisine, an id for the recipe, and the ingredients.

As a first step, let's look at the cuisines in the dataset. How many and how much of these do we have?

%matplotlib inline

import matplotlib.pyplot as plt
plt.style.use('ggplot')

df_train['cuisine'].value_counts().plot(kind='bar')

<matplotlib.axes._subplots.AxesSubplot at 0x10dce51d0>

As can be seen in this figure, there are a lot of Italian, Mexican and Southern US recipes, a little less of the other recipes.

To get a little insight in the data itself, we can look at a couple of recipes. In particular, we can count the most frequent ingredients for each cuisine. To do that, we can use the Python counter objects (found in the collections module from the standard library).

from collections import Counter

counters = {}
for cuisine in df_train['cuisine'].unique():
    counters[cuisine] = Counter()
    indices = (df_train['cuisine'] == cuisine)
    for ingredients in df_train[indices]['ingredients']:
        counters[cuisine].update(ingredients)

Let's look at a result:

counters['italian'].most_common(10)

[('salt', 3454),
 ('olive oil', 3111),
 ('garlic cloves', 1619),
 ('grated parmesan cheese', 1580),
 ('garlic', 1471),
 ('ground black pepper', 1444),
 ('extra-virgin olive oil', 1362),
 ('onions', 1240),
 ('water', 1052),
 ('butter', 1030)]

We can easily convert the top 10 ingredients for each cuisine to a separate dataframe for nicer viewing:

top10 = pd.DataFrame([[items[0] for items in counters[cuisine].most_common(10)] for cuisine in counters],
            index=[cuisine for cuisine in counters],
            columns=['top{}'.format(i) for i in range(1, 11)])
top10

	top1	top2	top3	top4	top5	top6	top7	top8	top9	top10
jamaican	salt	onions	water	garlic	ground allspice	pepper	scallions	dried thyme	black pepper	garlic cloves
moroccan	salt	olive oil	ground cumin	onions	ground cinnamon	garlic cloves	water	ground ginger	carrots	paprika
irish	salt	all-purpose flour	butter	onions	potatoes	sugar	baking soda	baking powder	milk	carrots
russian	salt	sugar	onions	all-purpose flour	sour cream	eggs	water	butter	unsalted butter	large eggs
greek	salt	olive oil	dried oregano	garlic cloves	feta cheese crumbles	extra-virgin olive oil	fresh lemon juice	ground black pepper	garlic	pepper
french	salt	sugar	all-purpose flour	unsalted butter	olive oil	butter	water	large eggs	garlic cloves	ground black pepper
italian	salt	olive oil	garlic cloves	grated parmesan cheese	garlic	ground black pepper	extra-virgin olive oil	onions	water	butter
korean	soy sauce	sesame oil	garlic	green onions	sugar	salt	water	sesame seeds	onions	scallions
thai	fish sauce	garlic	salt	coconut milk	vegetable oil	soy sauce	sugar	water	garlic cloves	fresh lime juice
vietnamese	fish sauce	sugar	salt	garlic	water	carrots	soy sauce	shallots	garlic cloves	vegetable oil
southern_us	salt	butter	all-purpose flour	sugar	large eggs	baking powder	water	unsalted butter	milk	buttermilk
cajun_creole	salt	onions	garlic	green bell pepper	butter	olive oil	cayenne pepper	cajun seasoning	all-purpose flour	water
indian	salt	onions	garam masala	water	ground turmeric	garlic	cumin seed	ground cumin	vegetable oil	oil
british	salt	all-purpose flour	butter	milk	eggs	unsalted butter	sugar	onions	baking powder	large eggs
mexican	salt	onions	ground cumin	garlic	olive oil	chili powder	jalapeno chilies	sour cream	avocado	corn tortillas
brazilian	salt	onions	olive oil	lime	water	garlic cloves	garlic	cachaca	sugar	tomatoes
spanish	salt	olive oil	garlic cloves	extra-virgin olive oil	onions	water	tomatoes	ground black pepper	red bell pepper	pepper
filipino	salt	garlic	water	onions	soy sauce	pepper	oil	sugar	carrots	ground black pepper
chinese	soy sauce	sesame oil	salt	corn starch	sugar	garlic	water	green onions	vegetable oil	scallions
japanese	soy sauce	salt	mirin	sugar	water	sake	rice vinegar	vegetable oil	scallions	ginger

An even better visualisation would be to have images instead of words for this visualization. We can do this by exporting the previous table to html and replacing the ingredient names with HTML image tags for the selected ingredients. This is done using regular expression matching, while the image is base64 encoded in the source (thanks).

import re
import base64

import pdb

def repl(m):
    ingredient = m.groups()[0]
    image_path = 'img/' + ingredient + '.png'
    with open(image_path, "rb") as image_file:
        encoded_string = base64.b64encode(image_file.read())
    return '<td><img width=100 src="data:image/png;base64,{}"></td>'.format(encoded_string.decode('utf-8'))

table_with_images = re.sub("<td>([ \-\w]+)</td>", repl, top10.to_html())

We can easily display this HTML output in our notebook:

from IPython.display import HTML

HTML(table_with_images)

	top1	top2	top3	top4	top5	top6	top7	top8	top9	top10
jamaican
moroccan
irish
russian
greek
french
italian
korean
thai
vietnamese
southern_us
cajun_creole
indian
british
mexican
brazilian
spanish
filipino
chinese
japanese

This visualization allows us to determine a couple of things. For instance we can see that the top1 ingredient for each cuisine is a salty ingredient. This salty ingredient allows us to group the cuisines already:

• salt is the standard for most cuisines
• soy sauce is number one for chinese, japanese and korean cuisines
• fish sauce is number one for thai and vietnamese cuisines

Another things that is easily seen from this table is that many ingredients have more than one name:

• garlic cloves, garlic
• olive oil, extra-virgin olive oil
• ...

Jugding from this table, it can be interesting to see which ingredients among the top10 ingredients are highly specific for a certain cuisine. A way to do this is to simply count the number of times an ingredient appears in a given cuisine and divide by the total number of recipes.

To do this, we first create a new column in our dataframe by simply concatening the ingredients to a single string:

df_train['all_ingredients'] = df_train['ingredients'].map(";".join)

df_train.head()

	cuisine	id	ingredients	all_ingredients
0	greek	10259	[romaine lettuce, black olives, grape tomatoes...	romaine lettuce;black olives;grape tomatoes;ga...
1	southern_us	25693	[plain flour, ground pepper, salt, tomatoes, g...	plain flour;ground pepper;salt;tomatoes;ground...
2	filipino	20130	[eggs, pepper, salt, mayonaise, cooking oil, g...	eggs;pepper;salt;mayonaise;cooking oil;green c...
3	indian	22213	[water, vegetable oil, wheat, salt]	water;vegetable oil;wheat;salt
4	indian	13162	[black pepper, shallots, cornflour, cayenne pe...	black pepper;shallots;cornflour;cayenne pepper...

We can now take advantage of the powerful string processing functions of pandas to check for the presence of an ingredient in a recipe:

df_train['all_ingredients'].str.contains('garlic cloves')

0        False
1        False
2        False
3        False
4        False
5        False
6        False
7        False
8        False
9        False
10       False
11       False
12        True
13       False
14       False
15       False
16       False
17       False
18       False
19       False
20       False
21       False
22       False
23       False
24       False
25       False
26       False
27       False
28       False
29       False
         ...  
39744     True
39745    False
39746    False
39747    False
39748    False
39749    False
39750    False
39751    False
39752    False
39753     True
39754     True
39755    False
39756    False
39757     True
39758    False
39759    False
39760    False
39761     True
39762    False
39763    False
39764    False
39765    False
39766    False
39767    False
39768    False
39769    False
39770    False
39771    False
39772    False
39773    False
Name: all_ingredients, dtype: bool

This can be used to group our recipes by the presence of that ingredient:

indices = df_train['all_ingredients'].str.contains('garlic cloves')
df_train[indices]['cuisine'].value_counts().plot(kind='bar',
                                                 title='garlic cloves as found per cuisine')

<matplotlib.axes._subplots.AxesSubplot at 0x10df36c18>

However, we have to keep in mind that there are a lot of Italian recipes in our database, so it's appropriate to divide by that number before presenting the result:

relative_freq = (df_train[indices]['cuisine'].value_counts() / df_train['cuisine'].value_counts())
relative_freq.sort(inplace=True)
relative_freq.plot(kind='bar')

/Users/kappamaki/anaconda/lib/python3.4/site-packages/ipykernel/__main__.py:2: FutureWarning: sort is deprecated, use sort_values(inplace=True) for for INPLACE sorting
  from ipykernel import kernelapp as app

<matplotlib.axes._subplots.AxesSubplot at 0x10e036630>

This way of looking at the data lets us see which countries use garlic cloves a lot in the recipes found in the database. As expected, mediterranean and asian cuisines are at the top, and british at the bottom.

We can do this sort of plot for all top 10 ingredients. First let's determine the unique ingredients:

import numpy as np
unique = np.unique(top10.values.ravel())
unique

array(['all-purpose flour', 'avocado', 'baking powder', 'baking soda',
       'black pepper', 'butter', 'buttermilk', 'cachaca',
       'cajun seasoning', 'carrots', 'cayenne pepper', 'chili powder',
       'coconut milk', 'corn starch', 'corn tortillas', 'cumin seed',
       'dried oregano', 'dried thyme', 'eggs', 'extra-virgin olive oil',
       'feta cheese crumbles', 'fish sauce', 'fresh lemon juice',
       'fresh lime juice', 'garam masala', 'garlic', 'garlic cloves',
       'ginger', 'grated parmesan cheese', 'green bell pepper',
       'green onions', 'ground allspice', 'ground black pepper',
       'ground cinnamon', 'ground cumin', 'ground ginger',
       'ground turmeric', 'jalapeno chilies', 'large eggs', 'lime', 'milk',
       'mirin', 'oil', 'olive oil', 'onions', 'paprika', 'pepper',
       'potatoes', 'red bell pepper', 'rice vinegar', 'sake', 'salt',
       'scallions', 'sesame oil', 'sesame seeds', 'shallots', 'sour cream',
       'soy sauce', 'sugar', 'tomatoes', 'unsalted butter',
       'vegetable oil', 'water'], dtype=object)

Turns out we can fit this in a 8 by 8 subplot diagram:

fig, axes = plt.subplots(8, 8, figsize=(20, 20))
for ingredient, ax_index in zip(unique, range(64)):
    indices = df_train['all_ingredients'].str.contains(ingredient)
    relative_freq = (df_train[indices]['cuisine'].value_counts() / df_train['cuisine'].value_counts())
    relative_freq.plot(kind='bar', ax=axes.ravel()[ax_index], fontsize=7, title=ingredient)

The previous diagram, even if it's not very clear, allows us to spot ingredients which have a high degree of uniqueness. Among them, I'd list:

• soy sauce (asian cuisine)
• sake (Japanese)
• sesame oil (asian cuisine)
• feta cheese crumbs (Greek)
• garam masala (Indian)
• ground ginger (Morrocan)
• avocado (Mexican)

Others are quite common:

• salt
• oil
• pepper
• sugar

This nicely concludes our data exploration. At the same time, it allows us to form a little intuition about how we could categorize a recipe's cuisine based on the ingredients:

• are there highly specific ingredients in the recipe that clearly point it to a given country?

In the next section, we will train a logistic regression classifier on the data we have analyzed so far and look at the results.

Training a logistic regression classifier

We will use scikit-learn to perform our classification. First, we will need to encode our features to a matrix that the machine learning algorithms in scikit learn can use. This is done using a count vectorizer:

from sklearn.feature_extraction.text import CountVectorizer

We can conveniently tell the count vectorizer which features it should accept and let him build the matrix with 1s and 0s when ingredients are present in a single step as follows:

cv = CountVectorizer()

X = cv.fit_transform(df_train['all_ingredients'].values)

We can check the shape of that matrix:

X.shape

(39774, 3010)

We see that the vectorizer has retained 3010 ingredients and processed the 40 000 recipes in the training dataset. We can easily access the features to check them using the vectorizers properties (which is a dictionary):

print(list(cv.vocabulary_.keys())[:100])

['lipton', 'hand', 'branzino', 'mayonnaise', 'tip', 'gouda', 'tamarind', 'meat', 'lea', 'saltine', 'style', 'ajinomoto', 'greek', 'chuck', 'ducklings', 'korean', 'tokyo', 'tender', 'shoots', 'prik', 'bitters', 'believ', 'satsuma', 'cardamon', 'pilaf', 'roll', 'crusts', 'brisée', 'penn', 'tamale', 'boneless', 'skate', 'picante', 'raw', 'swerve', 'sponge', 'filling', 'choi', 'sharp', 'cranberry', 'salt', 'manicotti', 'atar', 'quorn', 'ale', 'pound', 'nectar', 'iron', 'licorice', 'daiya', 'mince', 'chiffonade', 'japanese', 'yuzu', 'fleshed', 'picholine', 'ragu', 'buds', 'loosely', 'peppermint', 'cashews', 'yaki', 'stir', 'nam', 'blackberries', 'heirloom', 'terrine', 'crumbles', 'bonnet', 'clam', 'katsuo', 'cauliflowerets', 'crust', 'callaloo', 'doughs', 'wraps', 'pimentos', 'shaved', 'oregano', 'tomatillo', 'lump', 'cups', 'marin', 'olives', 'nectarines', 'greekstyl', 'bottom', 'fresca', 'cardoons', 'dijonnaise', 'delicata', 'lite', 'accompaniment', 'sprouts', 'flora', 'sansho', 'groundnut', 'seitan', 'tapioca', 'short']

Each feature gets assigned a column number, which is assigned a 1 or a 0 depending on the presence or not of the ingredient.

Now that we have our feature matrix, we still need to encode the labels that represent the cuisine of each recipe. This is done with a label encoder:

from sklearn.preprocessing import LabelEncoder

enc = LabelEncoder()
y = enc.fit_transform(df_train.cuisine)

The variable y is now a vector with number instead of strings for each cuisine:

y[:100]

array([ 6, 16,  4,  7,  7, 10, 17,  9, 13,  9,  9,  3,  9, 13,  9,  7,  1,
        9, 18, 19, 18, 13, 16,  3,  9,  3,  2,  9,  3, 13,  9,  2, 13, 18,
        9,  2,  9,  4, 16, 16,  9,  0, 13,  7, 13,  3,  5, 16, 16, 16, 11,
       16,  9, 16,  9, 10, 11,  7,  9,  8, 18, 18,  7, 10,  9, 18, 12,  5,
        5, 16, 17,  7, 14,  9,  9, 14, 14, 19, 11, 13,  2, 16,  5,  7,  7,
        9,  9,  7, 12, 17,  9, 16, 16,  6, 13, 13, 16,  7,  9,  9])

We can check the result by inspecting the encoders classes:

enc.classes_

array(['brazilian', 'british', 'cajun_creole', 'chinese', 'filipino',
       'french', 'greek', 'indian', 'irish', 'italian', 'jamaican',
       'japanese', 'korean', 'mexican', 'moroccan', 'russian',
       'southern_us', 'spanish', 'thai', 'vietnamese'], dtype=object)

Let's now train a logistic regression on the dataset. We'll split the dataset so that we can also test our classifier on data that he hasn't seen before:

from sklearn.cross_validation import train_test_split

X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2)

Now, let's train a logistic regression:

from sklearn.linear_model import LogisticRegression

logistic = LogisticRegression()
logistic.fit(X_train, y_train)

LogisticRegression(C=1.0, class_weight=None, dual=False, fit_intercept=True,
          intercept_scaling=1, max_iter=100, multi_class='ovr', n_jobs=1,
          penalty='l2', random_state=None, solver='liblinear', tol=0.0001,
          verbose=0, warm_start=False)

We can evaluate our classifier on our test set:

logistic.score(X_test, y_test)

0.77737272155876802

It turns out it performs quite nicely, with a 78% accuracy.

However, this doesn't tell the whole story about what's happening. Let's inspect the classification results using a confusion matrix.

Inspecting the classification results using a confusion matrix

A confusion matrix allows us to see the confusion the classifier makes. It should be read column by column. In each column, one sees the recipes the classifier considered to be one cuisine. Looking at the color in each square one can see the relative accuracy of that classification.

from sklearn.metrics import confusion_matrix

plt.figure(figsize=(10, 10))

cm = confusion_matrix(y_test, logistic.predict(X_test))
cm_normalized = cm.astype('float') / cm.sum(axis=1)[:, np.newaxis]

plt.imshow(cm_normalized, interpolation='nearest')
plt.title("confusion matrix")
plt.colorbar(shrink=0.3)
cuisines = df_train['cuisine'].value_counts().index
tick_marks = np.arange(len(cuisines))
plt.xticks(tick_marks, cuisines, rotation=90)
plt.yticks(tick_marks, cuisines)
plt.tight_layout()
plt.ylabel('True label')
plt.xlabel('Predicted label')

<matplotlib.text.Text at 0x119f8c208>

/Users/kappamaki/anaconda/lib/python3.4/site-packages/matplotlib/collections.py:590: FutureWarning: elementwise comparison failed; returning scalar instead, but in the future will perform elementwise comparison
  if self._edgecolors == str('face'):

Here, we see that some cuisines are really well predicted (Moroccan, Thai, Indian) while some suffer from confusion (Greek is often predicted as other cuisines, same with irish).

Another way to look at the results is the classification report from scikit-learn:

from sklearn.metrics import classification_report

y_pred = logistic.predict(X_test)
print(classification_report(y_test, y_pred, target_names=cuisines))

              precision    recall  f1-score   support

     italian       0.78      0.47      0.58        96
     mexican       0.58      0.41      0.48       165
 southern_us       0.80      0.66      0.73       289
      indian       0.78      0.85      0.82       542
     chinese       0.70      0.54      0.61       140
      french       0.62      0.63      0.63       555
cajun_creole       0.78      0.70      0.74       228
        thai       0.85      0.90      0.87       596
    japanese       0.69      0.47      0.56       123
       greek       0.80      0.89      0.84      1587
     spanish       0.84      0.73      0.78        97
      korean       0.81      0.72      0.76       289
  vietnamese       0.81      0.76      0.78       191
    moroccan       0.89      0.91      0.90      1262
     british       0.80      0.72      0.76       157
    filipino       0.57      0.40      0.47       100
       irish       0.69      0.81      0.74       860
    jamaican       0.67      0.50      0.57       195
     russian       0.74      0.72      0.73       321
   brazilian       0.69      0.48      0.57       162

 avg / total       0.77      0.78      0.77      7955

This allows use to see the different precision measurements (accuracy, recall, f1 score) all in a single place.

From the previous analyses, we can come up with a number of ways of how to improve aspects of our machine learning and reach better classification results.

Conclusions

In this post, we've gone through different stages of machine learning: we first explored the data in depth that came with the challenge and then went on to train a model, whose results we tried to analyze. It's not clear from the results what we can easily improve in our classification, but it gives us quite a lot of information to analyze.

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This article has been tagged with the following terms:

Machine Learning Kaggle

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