From the course: Introduction to jamovi

Dot plots - jamovi Tutorial

From the course: Introduction to jamovi

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Dot plots

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- [Josh Olenslager] Box plots and violin plots are a pretty nice way of summarizing the distribution of a quantitative and continuous variable, but maybe you actually want to see the data directly. And dot plots are a way that allow you to do that. And beginning with the violin plots that I made, using the IRS data from the example set, then I'm going to click on the analysis to open up the commands, and I'm going to come back down here to Plots. And I'll move this up, and what I'm going to do is simply add data. Now, a lot of times, you don't want to have things stacked where you have more than one kind of plot on top of another. The violin and the data, it works kind of well, because the violin's an empty shape, and here you have the data in there. Now, what this is, is every data point in the data set, there's 150 in this particular case, and they go from the lowest score up to the highest score. And you can see how they approximately match the density of the violin plot. Now, this is called a jittered chart. 'Cause really, every dot should be exactly on a line, here, in the middle, but that makes it hard to tell how many there are in a particular place, 'cause they might lay on top of one another. And so jittering is randomly spreading them out a little bit to the left and to the right, so they're not usually on top of each other, and it's a little easier to see the density of the distribution. I'll show you some others here. On the other hand, you have another choice. Instead of this jittering, if you're a nice and orderly person, you can also select stacked. And what stack does, is instead of distributing them out randomly, it puts them exactly where they need to go, and arranges them out in, mirror image patterns as you go up the chart. And so, again, this will appeal to those of you who are very fastidious, but now you can see a little clearer the distribution of points at each value. And you can see, really how the violin plot mimics that. I'm actually going to leave the violin plot on, normally I would remove it, because, the two go together nicely, they don't compete. And now we're going to come down here, to where we have our same violin plots, but broken down by the species. I'm going to click on that, bring up that analysis, and then I'll click on Data, and I'll leave it at Stacked. Now, what's interesting is, I said Stacked, but that appears to be Jitter, so I'm going to see if I can get its attention by switching back and forth from Jitter to Stacked and see if it changes anything. It was just a small glitch, but by going back and forth, we straightened it out. And now you can see how the data are arranged within each of the violin plots. And the height and the width of each of the violin plots now makes a little more sense. And so a dot plot of this kind, either Jittered or probably Stacked is a little easier to read, lets you see what's going into the box plots or into the violin plots, and lets you see the individual data points that are going to drive your analysis.

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