如何在箱线图上打印频率-ggplot-R

Question

This is my Dataframe

X color   cut      carrat
1   E    Ideal     0.23
2   J    Premiun   0.34
3   E    Ideal     0.23
...

I want to create a box plot of my column var "cut".

Here is the code for what I want to do...

ggplot(diamonds, aes(cut)) + geom_boxplot()

However, it isn't working properly as it's asking that aesthetics var "y", is missing.

It's because I am not providing a second var to aes, what's the second var I have to supply? Because I only need in the x's edge the different values my var "cut" can takes and in the Y's edge the frequendy of it.

Thanks.

Answer 1

The below code will do the job:

library(ggplot2)
p <- ggplot(diamonds, aes(x = cut, y=carat))
p <- p + geom_boxplot(outlier.colour = "blue", fill="grey85")
p <- p + labs(title = "Diamonds carats")
show(p)

a boxplot is a grouping of some data distributions, therefore you must provide the data whose distribution you want to boxplot. The x aesthetics must represent the type, the y must represent the data set.

Answer 2

A boxplot needs ay variable because it is illustrating a distribution. The count of rows by cut will not be a distribution but just one number per cut. Here are the counts of each cut:

> table(diamonds$cut)

     Fair      Good Very Good   Premium     Ideal 
     1610      4906     12082     13791     21551

That information can not be shown in a box plot. Instead, you could use a bar chart like so:

ggplot(diamonds, aes(x = cut)) +
  geom_bar()

Which produces this chart:

Or here is the code of a boxplot of cut and carat, as an example:

ggplot(diamonds, aes(x = cut, y = carat)) +
  geom_boxplot()

And the chart:

So the boxplot is showing the mean, range and quartiles of the carat column by each level of cut.