Operands Could not be Broadcast with Shapes (19,)(0,) -- KNN - numpy

Question

I am working on how to use KNN to predict a rating for a movie. I use a video and a book to teach myself how to go about it
I tried to run the code I found in the book but it gave me error message. I googled the error message so as to understand it and fix my problem but I don't think I know how to adapt the solutions to my problem.
import numpy as np
import pandas as pd
r_cols = ['user_id', 'movie_id', 'rating']
ratings = pd.read_csv('C:/Users/dell/Downloads/DataScience/DataScience-Python3/ml-100k/u.data', sep='\t', engine='python', names=r_cols, usecols=range(3)) # please enter your file path here. The file is u.data
print(ratings.head())
movieProperties = ratings.groupby('movie_id').agg({'rating': [np.size, np.mean]})
print(movieProperties.head())
movieNumRatings = pd.DataFrame(movieProperties['rating']['size'])
movieNormalizedNumRatings = movieNumRatings.apply(lambda x: (x - np.min(x)) / (np.max(x) - np.min(x)))
print(movieNormalizedNumRatings.head())
movieDict = {}
with open('C:/Users/dell/Downloads/DataScience/DataScience-Python3/ml-100k/u.item') as f: # The file is u.item
temp = ''
for line in f:
fields = line.rstrip('\n').split('|')
movieID = int(fields[0])
name = fields[1]
genres = fields[5:25]
genres = map(int, genres)
movieDict[movieID] = (name, genres, movieNormalizedNumRatings.loc[movieID].get('size'), movieProperties.loc[movieID].rating.get('mean'))
print(movieDict[1])
from scipy import spatial
def ComputeDistance(a, b):
genresA = np.array(list(a[1]))
genresB = np.array(list(b[1]))
genreDistance = spatial.distance.cosine(genresA, genresB)
popularityA = np.array(a[2])
popularityB = np.array(b[2])
popularityDistance = abs(popularityA - popularityB)
return genreDistance + popularityDistance
print(ComputeDistance(movieDict[2], movieDict[4]))
import operator
def getNeighbors(movieID, K):
distances = []
for movie in movieDict:
if (movie != movieID):
dist = ComputeDistance(movieDict[movieID], movieDict[movie])
distances.append((movie, dist))
distances.sort(key=operator.itemgetter(1))
neighbors = []
for x in range(K):
neighbors.append(distance[x][0])
return neighbors
K = 10
avgRating = 0
neighbors = getNeighbors(1, K)
I got this error message from PowerShell:
Traceback(most recent call last):
neighbors = getNeighbors(1, K)
dist = ComputeDistance(movieDict[movieID], movieDict[movie])
genreDistance = spatial.distance.cosine(genresA, genresB)
return correlation(u, v, w=w, centered=False)
uv = np.average(u*v, weights=w)
ValueError: operands could not be broadcast together with shape (19,)(0,)
I got this error message when I tried to debug the problem from ipython terminal:
c:\programdata\anaconda3\lib\site-packages\scipy\spatial\distance.py(695)correlation()
693 u = u - umu
694 v = v - vmu
---> 695 uv = np.average(u*v, weights=w)
696 uu = np.average(np.square(u), weights=w)
697 vv = np.average(np.square(v), weights=w)
**Note**: The code ran fine and produced results up until *print(Cprint(ComputeDistance(movieDict[2], movieDict[4]))*
My guess is the problem is with this part of the code:
import operator
def getNeighbors(movieID, K):
distances = []
for movie in movieDict:
if (movie != movieID):
dist = ComputeDistance(movieDict[movieID], movieDict[movie])
distances.append((movie, dist))
distances.sort(key=operator.itemgetter(1))
neighbors = []
for x in range(K):
neighbors.append(distance[x][0])
return neighbors
K = 10
avgRating = 0
neighbors = getNeighbors(1, K)
The code can be found in this link: https://hendra-herviawan.github.io/Movie-Recommendation-based-on-KNN-K-Nearest-Neighbors.html

Answer 1

The error of "operands could not be broadcast together with shape (x,)(y,)" usually raises when you are trying to perform an operation between two arrays that must have the same shape but they don't. In your case you are trying to take an weighted average between two arrays u and v. The arrays u and v don't have the length.
I saw that you parsing a movies list by splitting the lines with the "|" character and then storing these results in a dictionary. Probably this file or its division with "|" are returning different results.
The error log shows that the second array doesn't have any element, this could be generated by an empty line on the movies files.