Each line contains 72 temperature values for each of the 5° sections; there are 32 rows, one for each 5°s of latitude. Between each section is the month and year. -9999 is used to signal no data available. The temperatures are in degrees Celsius converted to integers (the counting numbers: 1, 2, 3, etc.) by multiplying by 100 — presumably to avoid those pesky decimal points.
So, what now?
Well, for quick sketch animations, I use processing.org, which is a java-based animation framework, which means I get to play with all the java data structures! So, I gotta read all that lovely data into some of them. But what and how?
Ok, I figure I'll be rendering the temperatures onto a map of somesort, which means I'll need to read the data so I can get all the months' temperatures all at once. Basically, given a year and month, I need the temperatures.
Uh oh! I'm going to start to get a tad techie below, if that floats your boat then please continue, if you're a keen learner then I'll assume you've had a go at processing's excellent tutorials otherwise you can skip to the end to see the pretty teaser animation!
Well, the temperatures are in a two-dimensional grid. So, that pretty much calls for a two-dimensional array, which is a way of storing stuff in memory, just like a grid.
int[][] temperature;
The square brackets there indicate, in a cack-handed kind of way, that temperature has two dimensions. So far so good.
But I'm going to need 1,656 of them! One for each month of each year between 1880 and 2017. So, why not add a third dimension? Indeed, I could and just number the months 0 - 1,655, and it'd work just fine. But that's not very interesting. I need a challenge — I mean, it's Sunday afternoon coding for goodness sake!
What I chose to use was a HashMap for no other reason than I get to use generics! A hash map is a data structure that behaves kinda like an array, but the index can be anything you like and it doesn't need to be sequential. (In this case, I can actually just use integers, and they'd be sequential — I'm a sucker for punishment.)
I defined the HashMap like so:
HashMap<String, int[][]> data;
Much more interesting than a dull old multidimensional array! So what's going on here? What's with the angle brackets?
This type of data structure is known as a generic. Which means it can use any type of data; strings (basically, sequences of characters, AKA words and sentences), integers, objects (computery type objects, not those things on your table over there), etc. In this case I'm using a String and a two-dimensional array of integers, which I've listed inside the angle brackets. The first item is what is known as the "key" and the second is the "value."
I figured I could make the key something like "{month} {year}" eg: "7 1956" for July 1956, which would return the temperature grid for that month and year like so:
int[][] temperatureGrid = data.get("7 1956");So, how do you get the data in there?
Well, first I can't really use the pretty data file, as it is much easier to have a single character to separate the data values, such as a tab. As you can see here in this close up there are multiple space characters between the values (the little grey dots).
