I am from electrical engineering background and I want to do PhD in machine learning. But machine learning is a multi-disciplinary field and available in many departments. So I am bit confused that from which department I should pursue PhD and what is the difference in PhD programs in different departments. Should I pursue PhD in machine learning in computer science department or from electrical departments. Thanks.
Firstly, keep in mind that some institutions actually have their own machine learning departments (for example, Carnegie Mellon University). That being said, in general, Machine Learning falls under the umbrella of Computer Science and Statistics / Applied Math. It's typically not considered a subset of Electrical Engineering unless you're working in robotics or very narrow cases of building specialized hardware for machine learning algorithms.
If you are interested in doing a PhD in machine learning, you will most likely be applying to either a Computer Science, Applied Mathematics, or Robotics program.