Python Error: x and y must have same first dimension, but have shapes (8,) and (1,)

Question

# I'm trying to read the data given by python and apply KNN. However my graph has no data and I get ax and y must have same first dimension, but have shapes (8,) and (1,) error.

# I have tried using .shape to no luck.

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

plt.style.use('ggplot')

df = pd.read_csv  ('/content/heart.csv')
df.head()
df.shape

x = df.drop('target', axis=1).values
y = df['target'].values   

from sklearn.model_selection import train_test_split
x_train,x_test,y_train,y_test = train_test_split(x,y, test_size=0.4,random_state=42, stratify=y)

from sklearn.neighbors import KNeighborsClassifier
neighbors = np.arange(1,9)
train_accuracy = np.empty(len(neighbors))
test = np.empty(len(neighbors))

knn = KNeighborsClassifier(n_neighbors=2)
knn.fit(x_train, y_train)
train_accuracy = knn.score(x_train,y_train)
test_accuracy = knn.score(x_test, y_test)

test_accuracy = knn.score(x_test, y_test) 
plt.title('k-NN Varying number of neighbors')
plt.plot(neighbors, test_accuracy, label='Testing Accuracy')
plt.plot(neighbors, train_accuracy, label='Training Accuracy')
plt.legend()
plt.xlabel('Number of neighbors')
plt.ylabel('Accuracy')
plt.show()


Should plot a graph,

however, the graph has no info on it.

Answer 1

The shapes (8,) and (1,) error is because you are trying to plot a graph with neighbors (numpy array) on x-axis which has 8 values inside it and test_accuracy on y-axis which has only one value the score . This graph doesn't make sense and cannot be plotted. I'm not sure what you are trying to achieve in the program. Can you update with the result you want?