In this video, make sure you define the X's like so. I flipped the last two lines by mistake:

X = np.array(df.drop(['label'],1))
X = preprocessing.scale(X)
X_lately = X[-forecast_out:]
X = X[:-forecast_out:]

To forecast out, we need some data. We decided that we're forecasting out 10% of the data, thus we will want to, or at least *can* generate forecasts for each of the final 10% of the dataset. So when can we do this? When would we identify that data? We could call it now, but consider the data we're trying to forecast is not scaled like the training data was. Okay, so then what? Do we just do preprocessing.scale() against the last 10%? The scale method scales based on all of the known data that is fed into it. Ideally, you would scale both the training, testing, AND forecast/predicting data all together. Is this always possible or reasonable? No. If you can do it, you should, however. In our case, right now, we can do it. Our data is small enough and the processing time is low enough, so we'll preprocess and scale the data all at once.

In many cases, you wont be able to do this. Imagine if you were using gigabytes of data to train a classifier. It may take days to train your classifier, you wouldn't want to be doing this every...single...time you wanted to make a prediction. Thus, you may need to either NOT scale anything, or you may scale the data separately. As usual, you will want to test both options and see which is best in your specific case.

With that in mind, let's handle all of the rows from the definition of X onward.
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1. Introduction to Machine Learning
2. Regression Intro
3. Regression Features and Labels
4. Regression Training and Testing
5. Regression forecasting and predicting
6. Pickling and Scaling
7. Regression How it Works
8. How to program the Best Fit Slope
9. How to program the Best Fit Line
10. R Squared Theory
11. Programming R Squared
12. Testing Assumptions
13. Classification w/ K Nearest Neighbors Intro
14. K Nearest Neighbors Application
15. Euclidean Distance
16. Creating Our K Nearest Neighbors A
17. Writing our own K Nearest Neighbors in Code
18. Applying our K Nearest Neighbors Algorithm
19. Final thoughts on K Nearest Neighbors
20. Support Vector Machine Intro and Application
21. Understanding Vectors
22. Support Vector Assertion
23. Support Vector Machine Fundamentals
24. Support Vector Machine Optimization
25. Creating an SVM from scratch
26. SVM Training
27. SVM Optimization
28. Completing SVM from Scratch
29. Kernels Introduction
30. Why Kernels
31. Soft Margin SVM
32. Soft Margin SVM and Kernels with CVXOPT
33. SVM Parameters
34. Clustering Introduction
35. Handling Non-Numeric Data
36. K Means with Titanic Dataset
37. Custom K Means
38. K Means from Scratch
39. Mean Shift Intro
40. Mean Shift with Titanic Dataset
41. Mean Shift from Scratch
42. Mean Shift Dynamic Bandwidth

The objective of this course is to give you a holistic understanding of machine learning, covering theory, application, and inner workings of supervised, unsupervised, and deep learning algorithms.

In this series, we'll be covering linear regression, K Nearest Neighbors, Support Vector Machines (SVM), flat clustering, hierarchical clustering, and neural networks.