> I think the point is about how data manipulation is about 80% of machine learning work. If an algorithm is giving you crap results for some data set, once you

> I think the point is about how data manipulation is about 80% of machine learning work. If an algorithm is giving you crap results for some data set, once you've fiddled with its hyperparameters through cv and so on there's not much you can do besides data manipulations like PCA, ICA and the like, to try and get a better result. Data manipulation is different from data transformation. Manipulation changes the nature of data, transformation does not change the nature of data. PCA is data transformation, not data manipulation.