I have a question regarding machine learning. I mostly do exploratory data analysis (EDA) of large 'omics datasets. I recently submitted a metabolomics based manuscript, and one of the reviewers was not happy with my analysis of the data. I think he as misunderstood the concept of machine learning, but I could be mistaken. I have added one of many examples where he refer to machine learning.
Reviewer: "PCA, K-means, and any other machine learning multivariate method of analysis must be performed on sex-specific groups"
I have always believed that machine learning is used for classifying and prediction purposes, but I dont seem to find any clear definition. Anyhow, I have three questions:
- Can somebody define machine learning?
- Is PCA machine learning? I have always thought its a method of dimension reduction that seeks to explain observed variance? It does not care about labels or groupings, nor does it predict or classify anything. Can somebody explain me where I got this wrong?
- Is K means clustering per definition machine learning? This algorithm has been around since the late 60s, long before machine learning was even a thing. I understand that this algorithm is applied in machine learning, but so is linear regression and logistic regression - but we dont call that machine learning.
I would appreciate your input on this?