def storeFScores():
# load the prediction-ready training and testing data
trainData = pd.load('proc_data/prediction_ready_trainDat.pda')
testData = pd.load('proc_data/prediction_ready_testDat.pda')
trainData = trainData.dropna()
testData = testData.dropna()
# To answer question 5, we need to perform binary classification on 7 different sub-datasets.
# We will use Hector's decision trees, and for each case we will get both the true and the predicted ratings
# and extract the bootstrapped F-score. As a beginning experiment, we will consider K = 10 folds
# per bootstrap evaluation.
FScoreMeansAndVars = list(
) # a list of (mean, stdev) tuples that might prove handy
# We have 7 different feature vectors for both training and testing data
# that we need to consider, which we now put in the following two lists.
trainFeatVecs = [
trainData.ix[:, :23], # content-based system (user + item features)
trainData.ix[:, (22, 24)], # using only item-item predicted ratings
trainData.ix[:, (22, 23)], # using only user-user predicted ratings
trainData.
ix[:, 22:25], # using both item-item and user-user predicted ratings
trainData.ix[:, :23].join(
trainData.ix[:, 24:25]
), # content-based + item-item predicted ratings
trainData.ix[:, :23].join(
trainData.ix[:, 23:24]
), # content-based + user-user predicted ratings
trainData.ix[:, :23].join(
trainData.ix[:, 23:25]) # content-based + both predicted ratings
]
testFeatVecs = [
testData.ix[:, :23], # content-based system (user + item features)
testData.ix[:, (22, 24)], # using only item-item predicted ratings
testData.ix[:, (22, 23)], # using only user-user predicted ratings
testData.
ix[:, 22:25], # using both item-item and user-user predicted ratings
testData.ix[:, :23].join(
testData.ix[:,
24:25]), # content-based + item-item predicted ratings
testData.ix[:, :23].join(
testData.ix[:,
23:24]), # content-based + user-user predicted ratings
testData.ix[:, :23].join(
testData.ix[:, 23:25]) # content-based + both predicted ratings
]
# Now that we have all 7 different training and testing datasets,
# we can compute the bootstrapped F-score for every setup.
# We will store these bootstrapped F-scores in a list, which we will
# then store on disk for easy future access. We will
# use K=100 folds for our experiments.
for i in range(len(trainFeatVecs)):
print "Training decision tree for configuration %d." % (i + 1)
tree = get_tree(trainFeatVecs[i], 'isgood')
print "Trained a decision tree, found an optimal depth of: %d" % (
tree.optimal_depth)
print "Getting predictions of decision tree on testing data."
predictions = tree.predict(testFeatVecs[i])
print "Computing bootstrapped F-score."
mean, stddev = bootStrapEval(testFeatVecs[i]['isgood'].values,
predictions, 1000)
print "Computed a mean F-score of %.4f with a std. dev. of %.4f." % (
mean, stddev)
print "Storing bootstrapped F-score of configuration %d in a list." % (
i + 1)
FScoreMeansAndVars.append((mean, stddev))
print "Storing all F-scores on disk."
fp = open('proc_data/bootstrappedFScores.pda', 'wb')
pkl.dump(FScoreMeansAndVars, fp)
fp.close()
def bootStrapEval(trueLabs, predictedLabs, K, bag=False, dataset=None):
'''
This method has two different usages, which are disambiguated between by its boolean
4th argument, "bag".
1) If bag = false (the default), bootstrap evaluation is implemented. The method takes
K different bootstrapped samples of its first two arguments (true and predicted labels)
and computes the F-score for each sample, which it then stores in a list. At the end of
the execution, it returns the mean and the variance of those F-scores. This is an encoding
of algorithm 10 at page 65 of CIML.
2) If bag = true, ensemble learning via bagging is implemented. This effectively draws
K bootstrapped samples (i.e samples with replacement) from the dataset pointed to by
the 5th argument and for each sample it trains a decision tree classifier. Every tree
is stored in a list, which is returned to the caller at the end of execution.
@param trueLabs: If bag == false, a list of length N representing the true labels of our data. None otherwise.
@param predictedLabs: If bag == false, a list of length N representing the predicted labels of our data. None otherwise.
@param K: If bag == false, the number of folds to perform over the labels. Otherwise, the number of
bootstrapped samples to draw from the training data.
@param bag: boolean flag. If false (the default), the method performs bootstrap resampling. If true,
the method performs bagging of decision trees.
@param dataset: by default, None. If bag == true, must be non-None (this is checked for), and is
a reference to a pandas.DataFrame which holds the training data to draw samples from.
@return: If bag == false, mean and standard deviation of "K" - many F-scores. Otherwise, list of
trained decision tree classifiers.
@raise LogicalError: If there is some inconsistency, among numerous possible, with respect to the
arguments provided in each case.
'''
# Because this method is quite complex, we need to make sure that
# the arguments provided to it are consistent with the context
# in which we want to use it. We therefore need to do some
# sanity checking.
if K == None or K == 0: # this is applicable in both usage contexts: we need K > 0
raise LogicalError, "Method %s: Please provide a positive integer for the K parameter." % inspect.stack(
)[0][3]
if bag == False: # need to check the validity of the two first arguments
if trueLabs == None or predictedLabs == None or len(
trueLabs) == 0 or len(predictedLabs) == 0:
raise LogicalError, "Method %s: Cannot compute bootsrapped F-score without true or predicted labels." % inspect.stack(
)[0][3]
if len(trueLabs) != len(predictedLabs):
raise LogicalError, "Method %s: Mismatch between amount of true and predicted labels." % inspect.stack(
)[0][3]
else: # need to check the validity of the last argument
if dataset is None or dataset.shape[0] == 0:
raise DatasetError, "Method %s: Caller provided a null or empty dataset." % inspect.stack(
)[0][3]
# Case 1: Bootstrap Resampling
if bag == False:
# Initialize algorithm
scores = list() # a list of F-scores, initially empty
numExamples = len(trueLabs)
# For every fold
for _i in range(K):
foldTrueLabels = list()
foldPredictedLabels = list()
# For every example
for _j in range(numExamples):
# retrieve and store true and predicted label of example
sampledExampleIndex = np.random.randint(
numExamples) # sample a random example from 0 up to N - 1
foldTrueLabels.append(trueLabs[sampledExampleIndex])
foldPredictedLabels.append(predictedLabs[sampledExampleIndex])
# Compute and store the F score for the current fold.
scores.append(
__computeFScore__(foldTrueLabels, foldPredictedLabels))
# Return mean and standard deviation of all F scores.
return np.mean(scores), np.std(scores)
# Case 2: Bagging of decision trees
else:
nexamples = dataset.shape[0]
# keep a list of all the decision tree classifiers
# that we will train
DTreeList = list()
# for every sample
for datasetSample in range(K):
# keep a list of every example that you sample.
# In Python terms, this is a list of Series, and
# we will convert it to a pandas.DataFrame after we
# complete our inner loop.
examplesInSample = list()
# Select N examples for our sub-dataset
# by sampling with replacement.
for _example in range(nexamples):
selectedExample = np.random.randint(0, nexamples)
examplesInSample.append(dataset.irow(selectedExample))
subDataset = pd.DataFrame(examplesInSample)
subDataset.index = np.arange(subDataset.shape[0])
# Train a decision tree classifier on the bootstrapped data
# and store it in a list.
print "Building random tree %d." % (datasetSample + 1)
tree = get_tree(subDataset, 'isgood')
#print "Tree number %d has an optimal depth of: %d" %(datasetSample+1, tree.optimal_depth)
DTreeList.append(tree)
# end for _datasetSample
return DTreeList
def adaboost(trainDat, K):
"""
Implement the ADABoost algorithm, as described in CIML, page 152.
@param trainDat: a pandas.DataFrame representing our training data.
@param K: the number of decision tree stumps that we would like to train.
@return --- a list of K decision tree stumps, trained on weighted data.
--- a list of K adaptive parameters, used on predictions alongside
the individual classifiers' predictions.
@raise LogicalError if K<= 0, None or not an int
@raise DatasetError if trainDat is None or empty
"""
if trainDat is None or len(trainDat) == 0:
raise DatasetError, "Method %s: Cannot train ADAboost on a null or empty dataset." %(inspect.stack()[0][3])
if K is None or K <= 0 or not isinstance(K, int):
raise LogicalError, "Method %s: Need to train a positive number of classifiers" %(inspect.stack()[0][3])
print "Starting AdaBoost algorithm."
# initialize uniform weights
exampleWeights = np.array([(1 / trainDat.shape[0]) for _x_ in range(trainDat.shape[0])])
# run main algorithm
classifierList = list()
adaptParams = list()
for k in range(K):
# train a decision tree stump on the weighted training data
print "Training stump #%d." %(k+1)
stump = get_tree(trainDat, 'isgood', exampleWeights, 1, 0)
classifierList.append(stump)
# Run predictions on weighted training data
print "Getting training data predictions for stump #%d." %(k+1)
predictions = stump.predict(trainDat)
# Compute training error
trueValues = trainDat['isgood'].values
if len(predictions) != len(trueValues):
raise LogicalError, "Method %s, model #%d: predictions have to be as many as the true labels." %(inspect.stack()[0][3], k + 1)
misclassifiedExampleWeights = [exampleWeights[n] for n in range(len(predictions)) if predictions[n] != trueValues[n]]
trainingError = np.sum(misclassifiedExampleWeights) # this is how we consider weighted training error in AdaBoost.
# Compute and store the "adaptive" parameter a(k)
currentAdaptParam = 0.5 * np.log((1 - trainingError) / trainingError)
#if type(currentAdaptParam) != float:
#raise LogicalError, "Method %s, model #%d: type of adaptive parameter was %s instead of float." %(inspect.stack()[0][3], k + 1, type(currentAdaptParam))
adaptParams.append(currentAdaptParam)
print "Computed adaptive parameter for classifier %d. It is equal to: %.4f" %(k+1, currentAdaptParam)
# Update and normalize example weights
# Note that this is not a dot product, but an element-wise multiplication.
exponent = -currentAdaptParam *np.array([trueValues[n] for n in range(trainDat.shape[0])])* np.array([predictions[n] for n in range(trainDat.shape[0])])
try:
len(exponent)
except TypeError:
raise LogicalError, "Method %s: \"exponent\" is not an iterable." %(inspect.stack()[0][3])
if len(exponent) != trainDat.shape[0]:
raise LogicalError, "Method %s: our derivation of \"exponent\" should've yielded a numpy.ndarray of size %d at this point." %(inspect.stack()[0][3], trainDat.shape[0])
multiplier = exampleWeights * np.exp(exponent)
try:
len(multiplier)
except TypeError:
raise LogicalError, "Method %s: \"multiplier\" is not an iterable." %(inspect.stack()[0][3])
if len(multiplier) != trainDat.shape[0]:
raise LogicalError, "Method %s: our derivation of \"multiplier\" should've yielded a numpy.ndarray of size %d at this point." %(inspect.stack()[0][3], trainDat.shape[0])
# Now we need to normalize, and God only knows how we're supposed to do this.
normalizer = np.sum(multiplier) # TODO: Decide whether this is the correct normalizer
exampleWeights = exampleWeights / normalizer
try:
len(exampleWeights)
except TypeError:
raise LogicalError, "Method %s, model #%d: after the update to \"exampleWeights\", this variable no longer represents a numpy.ndarray." %(inspect.stack()[0][3], k + 1)
if len(exampleWeights) != trainDat.shape[0]:
raise LogicalError, "Method %s, model #%d: the update to exampleWeights should've yielded a numpy.ndarray of size %d at this point." %(inspect.stack()[0][3], k + 1, trainDat.shape[0])
return classifierList, adaptParams
def adaboost(trainDat, K):
"""
Implement the ADABoost algorithm, as described in CIML, page 152.
@param trainDat: a pandas.DataFrame representing our training data.
@param K: the number of decision tree stumps that we would like to train.
@return --- a list of K decision tree stumps, trained on weighted data.
--- a list of K adaptive parameters, used on predictions alongside
the individual classifiers' predictions.
@raise LogicalError if K<= 0, None or not an int
@raise DatasetError if trainDat is None or empty
"""
if trainDat is None or len(trainDat) == 0:
raise DatasetError, "Method %s: Cannot train ADAboost on a null or empty dataset." % (
inspect.stack()[0][3])
if K is None or K <= 0 or not isinstance(K, int):
raise LogicalError, "Method %s: Need to train a positive number of classifiers" % (
inspect.stack()[0][3])
print "Starting AdaBoost algorithm."
# initialize uniform weights
exampleWeights = np.array([(1 / trainDat.shape[0])
for _x_ in range(trainDat.shape[0])])
# run main algorithm
classifierList = list()
adaptParams = list()
for k in range(K):
# train a decision tree stump on the weighted training data
print "Training stump #%d." % (k + 1)
stump = get_tree(trainDat, 'isgood', exampleWeights, 1, 0)
classifierList.append(stump)
# Run predictions on weighted training data
print "Getting training data predictions for stump #%d." % (k + 1)
predictions = stump.predict(trainDat)
# Compute training error
trueValues = trainDat['isgood'].values
if len(predictions) != len(trueValues):
raise LogicalError, "Method %s, model #%d: predictions have to be as many as the true labels." % (
inspect.stack()[0][3], k + 1)
misclassifiedExampleWeights = [
exampleWeights[n] for n in range(len(predictions))
if predictions[n] != trueValues[n]
]
trainingError = np.sum(
misclassifiedExampleWeights
) # this is how we consider weighted training error in AdaBoost.
# Compute and store the "adaptive" parameter a(k)
currentAdaptParam = 0.5 * np.log((1 - trainingError) / trainingError)
#if type(currentAdaptParam) != float:
#raise LogicalError, "Method %s, model #%d: type of adaptive parameter was %s instead of float." %(inspect.stack()[0][3], k + 1, type(currentAdaptParam))
adaptParams.append(currentAdaptParam)
print "Computed adaptive parameter for classifier %d. It is equal to: %.4f" % (
k + 1, currentAdaptParam)
# Update and normalize example weights
# Note that this is not a dot product, but an element-wise multiplication.
exponent = -currentAdaptParam * np.array([
trueValues[n] for n in range(trainDat.shape[0])
]) * np.array([predictions[n] for n in range(trainDat.shape[0])])
try:
len(exponent)
except TypeError:
raise LogicalError, "Method %s: \"exponent\" is not an iterable." % (
inspect.stack()[0][3])
if len(exponent) != trainDat.shape[0]:
raise LogicalError, "Method %s: our derivation of \"exponent\" should've yielded a numpy.ndarray of size %d at this point." % (
inspect.stack()[0][3], trainDat.shape[0])
multiplier = exampleWeights * np.exp(exponent)
try:
len(multiplier)
except TypeError:
raise LogicalError, "Method %s: \"multiplier\" is not an iterable." % (
inspect.stack()[0][3])
if len(multiplier) != trainDat.shape[0]:
raise LogicalError, "Method %s: our derivation of \"multiplier\" should've yielded a numpy.ndarray of size %d at this point." % (
inspect.stack()[0][3], trainDat.shape[0])
# Now we need to normalize, and God only knows how we're supposed to do this.
normalizer = np.sum(
multiplier) # TODO: Decide whether this is the correct normalizer
exampleWeights = exampleWeights / normalizer
try:
len(exampleWeights)
except TypeError:
raise LogicalError, "Method %s, model #%d: after the update to \"exampleWeights\", this variable no longer represents a numpy.ndarray." % (
inspect.stack()[0][3], k + 1)
if len(exampleWeights) != trainDat.shape[0]:
raise LogicalError, "Method %s, model #%d: the update to exampleWeights should've yielded a numpy.ndarray of size %d at this point." % (
inspect.stack()[0][3], k + 1, trainDat.shape[0])
return classifierList, adaptParams
def storeFScores():
# load the prediction-ready training and testing data
trainData = pd.load('proc_data/prediction_ready_trainDat.pda')
testData = pd.load('proc_data/prediction_ready_testDat.pda')
trainData = trainData.dropna()
testData = testData.dropna()
# To answer question 5, we need to perform binary classification on 7 different sub-datasets.
# We will use Hector's decision trees, and for each case we will get both the true and the predicted ratings
# and extract the bootstrapped F-score. As a beginning experiment, we will consider K = 10 folds
# per bootstrap evaluation.
FScoreMeansAndVars = list() # a list of (mean, stdev) tuples that might prove handy
# We have 7 different feature vectors for both training and testing data
# that we need to consider, which we now put in the following two lists.
trainFeatVecs = [
trainData.ix[:, :23], # content-based system (user + item features)
trainData.ix[:, (22, 24)], # using only item-item predicted ratings
trainData.ix[:, (22, 23)], # using only user-user predicted ratings
trainData.ix[:, 22:25], # using both item-item and user-user predicted ratings
trainData.ix[:, :23].join(trainData.ix[:, 24:25]), # content-based + item-item predicted ratings
trainData.ix[:, :23].join(trainData.ix[:, 23:24]), # content-based + user-user predicted ratings
trainData.ix[:, :23].join(trainData.ix[:, 23:25]) # content-based + both predicted ratings
]
testFeatVecs = [
testData.ix[:, :23], # content-based system (user + item features)
testData.ix[:, (22, 24)], # using only item-item predicted ratings
testData.ix[:, (22, 23)], # using only user-user predicted ratings
testData.ix[:, 22:25], # using both item-item and user-user predicted ratings
testData.ix[:, :23].join(testData.ix[:, 24:25]), # content-based + item-item predicted ratings
testData.ix[:, :23].join(testData.ix[:, 23:24]), # content-based + user-user predicted ratings
testData.ix[:, :23].join(testData.ix[:, 23:25]) # content-based + both predicted ratings
]
# Now that we have all 7 different training and testing datasets,
# we can compute the bootstrapped F-score for every setup.
# We will store these bootstrapped F-scores in a list, which we will
# then store on disk for easy future access. We will
# use K=100 folds for our experiments.
for i in range(len(trainFeatVecs)):
print "Training decision tree for configuration %d." %(i+1)
tree = get_tree(trainFeatVecs[i], 'isgood')
print "Trained a decision tree, found an optimal depth of: %d" %(tree.optimal_depth)
print "Getting predictions of decision tree on testing data."
predictions = tree.predict(testFeatVecs[i])
print "Computing bootstrapped F-score."
mean, stddev = bootStrapEval(testFeatVecs[i]['isgood'].values, predictions, 1000)
print "Computed a mean F-score of %.4f with a std. dev. of %.4f." %(mean, stddev)
print "Storing bootstrapped F-score of configuration %d in a list." %(i+1)
FScoreMeansAndVars.append((mean, stddev))
print "Storing all F-scores on disk."
fp = open('proc_data/bootstrappedFScores.pda', 'wb')
pkl.dump(FScoreMeansAndVars, fp)
fp.close()
def bootStrapEval(trueLabs, predictedLabs, K, bag = False, dataset = None):
'''
This method has two different usages, which are disambiguated between by its boolean
4th argument, "bag".
1) If bag = false (the default), bootstrap evaluation is implemented. The method takes
K different bootstrapped samples of its first two arguments (true and predicted labels)
and computes the F-score for each sample, which it then stores in a list. At the end of
the execution, it returns the mean and the variance of those F-scores. This is an encoding
of algorithm 10 at page 65 of CIML.
2) If bag = true, ensemble learning via bagging is implemented. This effectively draws
K bootstrapped samples (i.e samples with replacement) from the dataset pointed to by
the 5th argument and for each sample it trains a decision tree classifier. Every tree
is stored in a list, which is returned to the caller at the end of execution.
@param trueLabs: If bag == false, a list of length N representing the true labels of our data. None otherwise.
@param predictedLabs: If bag == false, a list of length N representing the predicted labels of our data. None otherwise.
@param K: If bag == false, the number of folds to perform over the labels. Otherwise, the number of
bootstrapped samples to draw from the training data.
@param bag: boolean flag. If false (the default), the method performs bootstrap resampling. If true,
the method performs bagging of decision trees.
@param dataset: by default, None. If bag == true, must be non-None (this is checked for), and is
a reference to a pandas.DataFrame which holds the training data to draw samples from.
@return: If bag == false, mean and standard deviation of "K" - many F-scores. Otherwise, list of
trained decision tree classifiers.
@raise LogicalError: If there is some inconsistency, among numerous possible, with respect to the
arguments provided in each case.
'''
# Because this method is quite complex, we need to make sure that
# the arguments provided to it are consistent with the context
# in which we want to use it. We therefore need to do some
# sanity checking.
if K == None or K == 0: # this is applicable in both usage contexts: we need K > 0
raise LogicalError, "Method %s: Please provide a positive integer for the K parameter." % inspect.stack()[0][3]
if bag== False: # need to check the validity of the two first arguments
if trueLabs == None or predictedLabs == None or len(trueLabs) == 0 or len(predictedLabs) == 0:
raise LogicalError, "Method %s: Cannot compute bootsrapped F-score without true or predicted labels." % inspect.stack()[0][3]
if len(trueLabs) != len(predictedLabs):
raise LogicalError, "Method %s: Mismatch between amount of true and predicted labels." % inspect.stack()[0][3]
else: # need to check the validity of the last argument
if dataset is None or dataset.shape[0] == 0:
raise DatasetError, "Method %s: Caller provided a null or empty dataset." % inspect.stack()[0][3]
# Case 1: Bootstrap Resampling
if bag == False:
# Initialize algorithm
scores = list() # a list of F-scores, initially empty
numExamples = len(trueLabs)
# For every fold
for _i in range(K):
foldTrueLabels = list()
foldPredictedLabels = list()
# For every example
for _j in range(numExamples):
# retrieve and store true and predicted label of example
sampledExampleIndex = np.random.randint(numExamples) # sample a random example from 0 up to N - 1
foldTrueLabels.append(trueLabs[sampledExampleIndex])
foldPredictedLabels.append(predictedLabs[sampledExampleIndex])
# Compute and store the F score for the current fold.
scores.append(__computeFScore__(foldTrueLabels, foldPredictedLabels))
# Return mean and standard deviation of all F scores.
return np.mean(scores), np.std(scores)
# Case 2: Bagging of decision trees
else:
nexamples = dataset.shape[0]
# keep a list of all the decision tree classifiers
# that we will train
DTreeList = list()
# for every sample
for datasetSample in range(K):
# keep a list of every example that you sample.
# In Python terms, this is a list of Series, and
# we will convert it to a pandas.DataFrame after we
# complete our inner loop.
examplesInSample = list()
# Select N examples for our sub-dataset
# by sampling with replacement.
for _example in range(nexamples):
selectedExample = np.random.randint(0, nexamples)
examplesInSample.append(dataset.irow(selectedExample))
subDataset = pd.DataFrame(examplesInSample)
subDataset.index = np.arange(subDataset.shape[0])
# Train a decision tree classifier on the bootstrapped data
# and store it in a list.
print "Building random tree %d." %(datasetSample + 1)
tree = get_tree(subDataset, 'isgood')
#print "Tree number %d has an optimal depth of: %d" %(datasetSample+1, tree.optimal_depth)
DTreeList.append(tree)
# end for _datasetSample
return DTreeList