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[No audio]

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Hi again, in this lecture, I'll show you

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how to make a country by population map.

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I'll be showing population of each

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country through graduated colors.

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So we'll think about a range of colors to

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represent population from low to high.

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And we have that piece of information in

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a world.json file, which is stored

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in this POP2005 attribute. So POP2005

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means population from 2005, which is

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quite old, but it shouldn't be a

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problem for educational purposes. So

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let's get back to the code, and the way

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to change the color of those polygons,

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because by default, we have this green

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color, and there's also transparency on the

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polygons. You can see the

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base map on the background, and so to change

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that, you need to access the style

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function argument. But I have missed

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something here from the previous

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lecture, we check could cause some

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problems later. This doesn't have to be

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in a round brackets, delete that.

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[No audio]

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One here as well.

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So we have 1, 2, 3 open brackets

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and 3 closing brackets. Now it

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should be fine. So we need to add another

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arguments to GeoJSON, this is the first

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argument. So data is the first argument

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which ends in here. So add there another

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style_function argument, and you can

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actually break the line in here. You are

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free to break lines in Python, when the

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expression is inside brackets, round

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brackets, square, or curly brackets. So in

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this case, this expression is inside

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brackets, so we are able to break it

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and it's going to break it at the comma.

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So style_function equals to.

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[No audio]

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Now this expects a lambda function. Lambda

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functions are just like functions,

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normal functions, but they are written in

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single lines of code. For instance,

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let's say l equals to lambda. This is a

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lambda function x, x a power of 2.

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Sorry, I had a typo there. Not lamdba

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but lambda, okay, another typo. All

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right. So l is a function here, just

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like you'd have a normal function, and

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then you can call l, you can pass a

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value like 5 and that will return

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5 in power of 2.

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So as you can see

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you can write the function in one single

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line and this can also be useful in

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other cases like this one in here that

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you'll see in just a bit. So lambda x.

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This also allows you to write anonymous

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functions. So this function now it

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doesn't have a name. Like here, I

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assigned a name to this function,

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because I needed to call it later. But

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this one here, we don't need to call it

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later. So you don't need to give a name.

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So here, the syntax would be correct if

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I do just like that. So let's go ahead and do this.

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[No audio]

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fillColor with a capital C, lowercase f,

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uppercase C, and that should be in quotes, let's say

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yellow.

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Now, if you want, you can leave it like that.

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So save the script.

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exit the python shell and execute the script.

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The execution went fine. Let me check the map, reload

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[No audio]

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and you'll see that colors of the polygons change to yellow.

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So that's how you can change the

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attributes of your JSON file. So this

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say basically you add another, basically

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you add in these attributes,

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which is not in the JSON file if you search for it.

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You'll find nothing and save.

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Now you can play around with this by adding

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conditionals inside this dictionary,

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such as if x

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properties

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POP2005

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[No audio]

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is less than, let's say 10 million.

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So 10 1, 2, 3, 1, 2, 3.

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So, what I'm doing here is

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I'm saying that set yellow to fillColor

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if x represent the feature,

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the JSON feature here. So if the property

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is actually at the POP2005 attribute

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of this attribute, of this attribute, which is

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here, this is POP2005. I know this is a bit complicated

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to Toggle Soft Wrap, so now I have all the text

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wraps here in the view. And here,

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POP2005, it's actually part of this

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dictionary, up to here. So this

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dictionary, these are a set of

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properties. This dictionary is the

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value of this key of the properties key.

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So, what that means is that, you know,

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we are accessing the value of a properties

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key using this syntax, which is known

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in Python. Meanwhile, x properties or

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that is, x here represents

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features. So you are accessing

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properties from features. And all

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background, this is a bit of a blackbox.

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But folium, what folium will do is it

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will go through all the features of all

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the polygons, and it will check if the

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value of POP2005 is less than 10

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million. And if it is, then it will set

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this color to fillColor attributes.

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That's more or less about it.

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I think it's better to put this green, so if

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it's less than 10 million, put it green, else,

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orange, if between

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10 million.

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Do the same thing here.

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Properties, actually, you can break the code in here.

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So properties POP2005.

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[No audio]

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Let's put here 20 million.

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So these are just arbitrary numbers, you can put

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everything that you want, but that will

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affect how your polygons are

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classified are colored. So for

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population between 10 million and 20

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million, we'll get orange colors.

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[No audio]

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else red, so everything above the new will be

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call it as a read. Okay, let me save

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this and so I hope this will work.

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[No audio]

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No errors. Reload.

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We have US color in red

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because it has a population of higher

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than 20 million people. And yeah, it

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seems to be working fine.

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[No audio]

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Yep, Portugal here. Portugal as a population of

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around 12 or 15 million people, I'm not

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sure. So it's in the middle range of our

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classification algorithm.

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[No audio]

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and it has more or less about it.

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And I'll talk to you later. Thanks.

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