Filtering RDDs and the minimum temperature by location example

Now we're going to introduce the concept of filters on RDDs, a way to strip down an RDD into the information we care about and create a smaller RDD from it. We'll do this in the context of another real example. We have some real weather data from the year 1800, and we're going to find out the minimum temperature observed at various weather stations in that year. While we're at it, we'll also use the concept of key/value RDDs as well as part of this exercise. So let's go through the concepts, walk through the code and get started.

What is filter()

Filter is just another function you can call on a mapper, which transforms it by removing information that you don't care about. In our example, the raw weather data actually includes things such as minimum temperatures observed and maximum temperatures for every day, and also the amount of precipitation observed for every day. However, all we care about for the problem we're trying to...