This is a Plot that is used to show only one variable

- can say that this is one-dimensional Scatter Plot

It also shows

- the mean of the distribution (as the "balanced point" of this distribution)

- The same, but the dots are stacked on top of each other
- As the number of values grows, it becomes harder to read
- Note that this gives us the same information as Histograms - but in there, the values are binned

In R, function `stripchart`

draws the dot plot

Example with `email50`

data from OpenIntro:

library(openintro) data(email50)

stripchart(email50$num_char, pch=19, col=rgb(0, 0, 1, 0.3), cex=1.5, axes=F, ylim=c(0.9, 1.5)) axis(side = 1) m = mean(email50$num_char) polygon(x=c(m-3, m, m+3), y=c(0.90, 0.95, 0.90), col="red")

Also we can add some jitter to have an idea of how many items we have in some area

set.seed(10) stripchart(email50$num_char, method="jitter", pch=19, col=rgb(0, 0, 1, 0.3), cex=1.5, axes=F, ylim=c(0.75, 1.6)) axis(side = 1) polygon(x=c(m-3, m, m+3), y=c(0.87, 0.95, 0.87) - 0.1, col="red")

Or can plot it vertically

stripchart(email50$num_char, method="jitter", vertical=T, pch=19, col=rgb(0, 0, 1, 0.3), cex=1.5)

To have a stacked plot, use `method="stack"`

stripchart(round(email50$num_char), method="stack", pch=19, col=rgb(0, 0, 1, 0.5), axes=F, ylim=c(0.8, 1.8)) axis(side = 1) polygon(x=c(m-3, m, m+3), y=c(0.87, 0.95, 0.87), col="red")

Note that it given similar information to a Histogram

- but the latter is binned, and this is not (so it looks rather as a Bar Chart)

t = table(round(email50$num_char)) a = rep(NA, 65) names(a) = 0:64 for (i in names(a)) { a[i] = t[i] } a[is.na(a)] = 0 barplot(a, ylim=c(-0.4, max(a))) polygon(x=c(m-3, m, m+3), y=c(-0.4, -0.05, -0.4), col="red")

hist(email50$num_char, breaks=30, col="red")

And finally, an example from [1]

set.seed(1) A = sample(0:10, 100, replace=T) stripchart(A, method="stack", offset=.5, at=.15, pch = 19, main = "Dotplot of Random Values", xlab = "Random Values")