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class SparseVector < Hash
def initialize
super
self.default = 0
end
def from_hash h
h.each_pair { |k,v| self[k] = v }
end
def sum
self.values.inject(:+)
end
def average
self.sum/self.size.to_f
end
def variance
avg = self.average
var = 0.0
self.values.each { |i| var += (avg - i)**2 }
return var
end
def stddev
Math.sqrt self.variance
end
def dot other
sum = 0.0
self.each_pair { |k,v| sum += v * other[k] }
return sum
end
def magnitude
Math.sqrt self.values.inject { |sum,i| sum+i**2 }
end
def cosinus_sim other
self.dot(other)/(self.magnitude*other.magnitude)
end
def euclidian_dist other
dims = [self.keys, other.keys].flatten.uniq
sum = 0.0
dims.each { |d| sum += (self[d] - other[d])**2 }
return Math.sqrt(sum)
end
end
def mean_sparse_vector array_of_vectors
mean = SparseVector.new
array_of_vectors.each { |i|
i.each_pair { |k,v|
mean[k] += v
}
}
n = array_of_vectors.size.to_f
mean.each_pair { |k,v| mean[k] = v/n }
return mean
end
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