ML/Data Mining/Big Data : Popular language for programming and community support
Python is gaining in popularity, has a lot of libraries, and is very useful for prototyping. I find that due to the many versions of python and its dependencies on C libs to be difficult to deploy though.
R is also very popular, has a lot of libraries, and was designed for data science. However, the underlying language design tends to make things overcomplicated.
Personally, I prefer Clojure because it has great data manipulation support and can interop with Java ecosystem. The downside of it currently is that there aren't too many data science libraries yet!
I am not sure if this question is correct, but I am asking to resolve the doubts I have.  

For Machine Learning/Data Mining, we need to learn about data, which means you need to learn Hadoop, which has implementation in Java for MapReduce(correct me if I am wrong).  
Hadoop also provides streaming api to support other languages(like python)  
Most grad students/researchers I know solve ML problems in python  
we see job posts for hadoop and Java combination very often  

I observed that Java and Python(in my observation) are most widely used languages for this domain.  

My question is what is most popular language for working on this domain.  
what factors involve in deciding which language/framework one should choose
I know both Java and python but confused always :

whether I start programming in Java(because of hadoop implementation)
whether I start programming in Python(because its easier and quicker to write)


This is a very open ended question, I am sure the advices might help me and people who have same doubt.
Thanks a lot in advance