What is the intuition behind number 1 and 2 when it comes to considering mean? And how will this affect performance and accuracy? 

Number 1:

```
    pca = decomposition.PCA(n_components=4)
    X_centered = X - X.mean(axis=0)
    pca.fit(X_centered)
    X_pca = pca.transform(X_centered)

```

Number 2:

```
    pca = decomposition.PCA(n_components=4)
    pca.fit(X)
    X_pca = pca.transform(X)

```

Thanks in advance