R for Data Science: Lunchbreak Lessons

- [Instructor] So you can see that I've created two vectors, one called x position, and one called y position. And this is an xy relationship. These are small vectors, but it's already pretty easy to get lost in how these vectors might relate to each other. And of course with that we should use some sort of a visual tool, like, let's try plots. So I type in P-L-O-T, and then I type x position and y POS, and I hit return.

And I get a graph that shows six points. Well, I can immediately see that there's more than six points in this graph. In fact, there are 13, x position and y position length is 13. But my graph is only showing six. I'm missing something. I'm not getting the full story. And to get a better picture of how these two relate I'm going to use something called a sunflower plot, which is a plot that's provided by r. To use sunflower plot the first thing I need to do is create an xy table.

So here's how I'll do that, xytabl, and into xytabl I'm going to place an xy table generated by using the xy table function against x position and y position. And I hit return, and I get a list of three, which by itself is not terribly revealing of any sort of relationships. But now when I use that information with sunflower plot, S-U-N-F-L-O-W-E-R P-L-O-T, and I call up xytabl, which is what I've just created.

And then I hit return. Now you can see that I have a new graph. And what's unique about this graph is we still have six points, but the first three points have veins against them, lines coming out of them. The first on has three lines, and the second has three lines, and the third one has four lines. Well, what that tells us is that at the 1,1 position there are three values. So if you look at xpos and ypos you'll see that the first set xpos is one, and ypos is one.

And then further on is another 1,1 combination. And I know there's three because the sunflower plot has indicated that there are three lines. The same thing for 2,1. If I look at 3,1 I should find four sets of that. And in fact, if you look at xpos vs ypos you'll find four combinations of three and one. So a sunflower plot is a really useful way to show how many combinations of values are in two compared vectors.