‫Welcome back.
‫I want to talk to you quickly about something called Matrix.
‫And a matrix is a way to describe 2D lists or multi dimensional lists.
‫What do I mean?
‫Well, I can create a matrix, and this is a name that I just made, so I can call it whatever I want.
‫But usually these are called matrix and programming.
‫And it looks something like this.
‫It's an array.
‫With another array inside of it.
‫So let's say, for example.
‫I have one, two, three here.
‫And then another array one or let's do two for.
‫Six.
‫And then another array.
‫Seven, eight, nine.
‫What's happening here?
‫Well, it's a two dimensional array.
‫We have the main array.
‫And then we have sub arrays, three arrays to be exact.
‫Now, why is this useful?
‫And by the way, this is two dimensional, but we can have multiple ones.
‫For example, you can have another array inside of this array.
‫But why is this important?
‫These type of matrices come up a lot in topics like machine learning or image processing.
‫For example, a computer doesn't really know what a photo of a dog is.
‫The only thing it understands is zeros and ones.
‫So a lot of photos.
‫For example, let's say we had a very simple photograph of a giant X, maybe this letter x.
‫Well, a computer can understand an image based on pixels on the screen, so maybe we can have zero,
‫one, zero.
‫100 or sorry, one here, zero here, and then one.
‫And right now, a computer can look at this.
‫And if this represented, let's say, a tiny little pixel here or maybe a pixel here on my screen,
‫the computer is going to say, oh, there's a one here.
‫So that means I should make this green in this corner, then dark here, then green, then dark green,
‫dark green, dark green.
‫And a computer is able to draw, let's say, an X.
‫And this is a simple example.
‫And using matrices, we can do a lot of these heavy calculations.
‫And that's how computers work underneath the hood when, let's say, for example, it's trying to display
‫something.
‫But the reason I wanted to talk about this here is when you want to access a multi dimensional list,
‫well, you would do something like this, let's say matrix.
‫Access the first item.
‫In The Matrix, which in this case will be this first array because it's the first item.
‫And then let's say we want to access the zero in here or let's change this to five.
‫Well, I'll do square brackets again and just do zero one.
‫So if I go.
‫One here, and let's print that out.
‫And I click Run.
‫I get five.
‫So it's accessing the first item in the array.
‫So it's going to look at the first order array, grab the first item which is right here, and then
‫grab the second item in that array.
‫So zero one, which is five.
‫And you can keep doing this.
‫If he had multi dimensional arrays, you can keep adding, keep adding, keep adding.
‫To access that information from an array or list.
‫But remember in Python, we want to use the term list.
‫I'll see you in the next one.
‫Bye bye.