transportation_prediction.py

# -*- coding: utf-8 -*-
"""
Created on Thu Dec 14 09:41:34 2017

@author: mounicm
"""

import pandas as pd
url = 'https://github.com/mounicmadiraju/scrape/blob/master/All_Cities_Malaysia_Singapore_Australia/results.json'
train = pd.read_json(url)


# before splitting anything, just predict the mean of the entire dataset
train['prediction'] = train.price.mean()
train


# calculate predictions
from sklearn import metrics
import numpy as np
np.sqrt(metrics.mean_squared_error(train.price, train.prediction))


# function that calculates the RMSE for a given split of miles
def mileage_split(miles):
    lower_mileage_price = train[train.miles < miles].price.mean()
    higher_mileage_price = train[train.miles >= miles].price.mean()
    train['prediction'] = np.where(train.miles < miles, lower_mileage_price, higher_mileage_price)
    return np.sqrt(metrics.mean_squared_error(train.price, train.prediction))


# calculate RMSE for tree which splits on miles < 50000
print 'RMSE:', mileage_split(50000)
train


# calculate RMSE for tree which splits on miles < 100000
print 'RMSE:', mileage_split(100000)
train


# check all possible mileage splits
mileage_range = range(train.miles.min(), train.miles.max(), 1000)
RMSE = [mileage_split(miles) for miles in mileage_range]


# allow plots to appear in the notebook
import matplotlib.pyplot as plt
plt.rcParams['figure.figsize'] = (6, 4)
plt.rcParams['font.size'] = 14


# plot mileage cutpoint (x-axis) versus RMSE (y-axis)
plt.plot(mileage_range, RMSE)
plt.xlabel('Mileage cutpoint')
plt.ylabel('RMSE (lower is better)')


# ## Building a regression tree in scikit-learn

# encode car as 0 and truck as 1
train['vtype'] = train.vtype.map({'car':0, 'train':1})


# define X and y
feature_cols = ['year', 'miles', 'doors', 'vtype']
X = train[feature_cols]
y = train.price


# instantiate a DecisionTreeRegressor (with random_state=1)
from sklearn.tree import DecisionTreeRegressor
treereg = DecisionTreeRegressor(random_state=1)
treereg


# use leave-one-out cross-validation (LOOCV) to estimate the RMSE for this model
from sklearn.cross_validation import cross_val_score
scores = cross_val_score(treereg, X, y, cv=14, scoring='mean_squared_error')
np.mean(np.sqrt(-scores))


# try different values one-by-one
treereg = DecisionTreeRegressor(max_depth=1, random_state=1)
scores = cross_val_score(treereg, X, y, cv=14, scoring='mean_squared_error')
np.mean(np.sqrt(-scores))

# list of values to try
max_depth_range = range(1, 8)

# list to store the average RMSE for each value of max_depth
RMSE_scores = []

# use LOOCV with each value of max_depth
for depth in max_depth_range:
    treereg = DecisionTreeRegressor(max_depth=depth, random_state=1)
    MSE_scores = cross_val_score(treereg, X, y, cv=14, scoring='mean_squared_error')
    RMSE_scores.append(np.mean(np.sqrt(-MSE_scores)))


# plot max_depth (x-axis) versus RMSE (y-axis)
plt.plot(max_depth_range, RMSE_scores)
plt.xlabel('max_depth')
plt.ylabel('RMSE (lower is better)')


# max_depth=3 was best, so fit a tree using that parameter
treereg = DecisionTreeRegressor(max_depth=3, random_state=1)
treereg.fit(X, y)


# "Gini importance" of each feature: the (normalized) total reduction of error brought by that feature
pd.DataFrame({'feature':feature_cols, 'importance':treereg.feature_importances_})

# create a Graphviz file
from sklearn.tree import export_graphviz
export_graphviz(treereg, out_file='tree_vehicles.dot', feature_names=feature_cols)


# read the testing data
url = 'https://github.com/mounicmadiraju/scrape/blob/master/All_Cities_Malaysia_Singapore_Australia/results.json'
test = pd.read_json(url)
test['vtype'] = test.vtype.map({'car':0, 'train':1})
test

# use fitted model to make predictions on testing data
X_test = test[feature_cols]
y_test = test.price
y_pred = treereg.predict(X_test)
y_pred

# calculate RMSE
np.sqrt(metrics.mean_squared_error(y_test, y_pred))


# calculate RMSE for your own tree!
y_test = [3000, 6000, 12000]
y_pred = [0, 0, 0]
from sklearn import metrics
np.sqrt(metrics.mean_squared_error(y_test, y_pred))

# fit a classification tree with max_depth=3 on all data
from sklearn.tree import DecisionTreeClassifier
treeclf = DecisionTreeClassifier(max_depth=3, random_state=1)
treeclf.fit(X, y)


# create a Graphviz file
export_graphviz(treeclf, out_file='tree_titanic.dot', feature_names=feature_cols)