Python Data Visualization Transcripts
Chapter: Matplotlib
Lecture: Scatter plots
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The next type of chart we'll talk about is a scatter plot. Let's get one started here. It's called scatter.
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And we're going to explicitly say what the X and Y axis are. In this case we want to plot the fuel cost versus the displacement.
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The other attribute I'd like to introduce is alpha, which is essentially how transparent the values are and we're going to pass in colors based
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on the number of cylinders. And while we're at it, let's go ahead and set some labels and titles.
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So now we have a nice scatter plot that shows us that as the engine displacement increases, the fuel cost increases which makes sense.
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A larger engine is going to use more fuel. The colors are telling us how many cylinders are in the engine.
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So we've got a lot of information that we're portraying in this plot.
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Let's go through another example of more customization that we can do on this plot and make it even more informative. So we'll keep the basic plot.
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Now we're going to set the X Label and the Y label and I'm going to show how to do that and increase
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the font size as well. We talked about using the formatter so let's format this access so it's a currency so maybe we show the dollar sign and a comma
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to make it a little easier to read. And for that we'll use the set major formatter.
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The other thing I'm gonna do to make it look a little cleaner is to change
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the font size and the rotation on our labels and we'll just change the label size on the Y axis And now I'm going to add a vertical line at $3500.
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So let's say part of our analysis is we have this target of $3500 that we're trying to get to or annotate on our graph.
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So this says axes vertical line. So we need to tell where to draw that line. We're gonna draw it at 3500, tell it we want to be black.
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We can tell what line style. There's a whole bunch of different line styles that matplot lib supports. Maybe we want to label this.
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So we'll have a line at 3500. So what this says is at a text annotation And we'll call the the text as target of 3500. The X.
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Y coordinates will pass a tuple of 3500 and 2. So it should be kind of right in here. Size of the text should be 16.
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And then the final thing I'm going to do is add a grid so we can see what it looks like. I think that looks nice.
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See if I made any typos forgot to tell it. Put the major formatter on the X axis spelled mis-spelled label size.
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And one of the other things I noticed now is I'd like to make this figure a little bit bigger. I think it's kind of cramped.
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So let's update this to fixed size. Will you run it? There we go. Now. We have a bigger figure. So let's walk through again. What we've done,
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We created our figure with one axis and the figure size is 9 by 7. We added a scatter plot. We the alpha is the transparency so that you can
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see more of the plots and the color is based on the cylinders. So notice that it's the displacement versus the fuel cost.
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But the cylinders are shown as the color. We set our X and Y labels. We included a size for the font to make it a little more readable.
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We set the formatter on the X axis so that the currency comes through with a dollar sign and a comma.
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We also set the tick parameters so we rotated the labels and the size. We added this vertical line on the chart That shows the target of 3500.
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And then we turned on the grid so this highlights all of the configuration options that you have available to you in matplot lib.
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And once you start to get the hang of it and start to look through the
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documentation. It's relatively straight forward but is verbose some of the future libraries that we'll be talking about to do make a lot of these easier.