 in this section we're going to look at collections. Now collections are really just groups of values like lists of values and those values could be numbers and they can be strings so they can be both numerical and take on some form of category so it's just lists of values. Now as per usual we're going to just see that the kernel has loaded properly and we see 2 plus 2 equals 4. Another thing that I want to introduce in this lesson is this very exciting section of code here where we're going to load a cascading style sheet file just to stylize our notebook a little bit. Some people like that it's quite easy to do for instance using the ipython kernel for the Jupyter notebooks but you can also do it right here in Julia. So I say file equals open and just it is in the current or present working directory this file style.css. I'll post these on github and other places as well so you can see what this cascading style sheet looks like it's going to load that. I'm going to create this computer variable called style and I'm going to say read all files to read everything in this open file and then I'm just going to call html and then in quotation marks here the dollar style so that just means read this variable which is just going to output this cascading style sheet to html. So if this doesn't make a lot of sense don't worry about it you can copy and paste this and just keep it at the top of all your files and as I say you've got to have this cascading style sheet. We're going to use some Google fonts that are freely available in the style sheet and as I said I'll give you a link to that let's just run that block of code and voila look at this isn't this a thing of beauty. So I've rendered a specific font for my writing my code here I've also got a specific font just here for my markdown output and if I double click on this you'll see it's still just I'm not using markdown I'm using html tags here to the matter heading one this says collections but it is rendered in a specific text as it is stated in this cascading style sheet. This cascading style sheet also gives this white background color this light gray background color you can change almost everything about your notebook just in a cascading style sheet. So if you know html and CSS you can really render some interesting notebooks. So apologies if you don't like this font I just chose it just because it's quite different from the default as you can see I've colorized it as well just a bit of contrast so you can see what this all is all about. So this chapter this lesson on collections lists of numerical or categorical values. The most common form of these are arrays as you can see there so in this lesson we're going to look at these arrays we're going to modify them we're gonna take add another dimension to them to have matrices we're gonna do a bit of set notation we're gonna look at two poles and we'll circle back to arrays we will bring it all together in the end. So without further ado in the next section let's start off by looking at arrays.