Size Issue when Plotting the Predicted Vaue

Question

I wrote a simple Stock Prediction Algorithm and got the predicted value. Then, I wanted to plot the relation between Adjusted close price and predicted value, but got the ValueError: x and y must be the same size. I tried to reshape it, but no luck. I'm having problem with the last 5 lines of the following code. How can I resize X and y_predict in order to have a same size of them? What is the exact problem with my resize code?

import quandl
import pandas as pd
import numpy as np
import datetime
import matplotlib.pyplot as plt
%matplotlib inline
from sklearn.linear_model import LinearRegression
from sklearn import preprocessing, svm, datasets
from sklearn.model_selection import cross_validate, train_test_split

stock_data = quandl.get("WIKI/AAPL")
stock_data = stock_data[["Adj. Close"]]
forecast_out = int(30)
stock_data["Prediction"] = stock_data[["Adj. Close"]].shift(-forecast_out)
X = np.array(stock_data.drop(['Prediction'],1))
X = preprocessing.scale(X)
X_forecast = X[-forecast_out]
X = X[:-forecast_out]
y = np.array(stock_data["Prediction"])
y = y[:-forecast_out]
LinearRegression().fit(X.reshape(-1,1),y)
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state = 0)
lin_reg = LinearRegression().fit(X_train,y_train)
y_predict = lin_reg.predict(X_test)

LinearRegression().fit(X.reshape(-1,1),y_predict)

plt.scatter(X_train, y_predict,  color='blue')
plt.plot(X_train, regr.coef_[0][0]*X_train + lin_reg.intercept_[0], '-r')
plt.xlabel("Adjusted closing price")
plt.ylabel("Predicted price")
```

Answer 1

You are using the full X dataset and want to plot it with the y_predict values, this is not possible since the size of both arrays is not the same. y_predict are the predicted values on X_test while X contains all inputs (i.e. X_train and X_test). You should therefore use X_test instead of X.