随着时间的推移，您将如何在 R 中为箱线图创建分类“箱”？

Question

Been working on this and haven't been able to find a decent answer.

Basically, I've got a dataset of NBA Player height vs draft year, and I am trying to create a boxplot to show how player height has changed overtime (this is for a hw assignment, so a boxplot is necessary). My dataset ( nba_data ) looks like the table below, but I have 10k rows ranging from players drafted in the 60s all the way to the 2000s.

player_name	draft_year	height_in
player_a	1998	76
player_b	1972	81
player_c	2012	79

So far the closest I've gotten is

ggplot(data = nba_data, aes(x = draft_year, 
                            y = height_in, 
                            group = cut(x = draft_year, breaks = 5)))  + 
  geom_boxplot()

And this is the result I get. As far as I understand, breaks being set to 5 should separate my years into 5 year buckets, right?

I created the same graph in Excel to get an idea of what it should look like:

I also attempted to create categories with cut, but was unable to apply it to my boxgraph. I mostly code in Python, but have to learn R for a class at school - any help is greatly appreciated.

Thanks!

Edit: Another question I guess would be how the "Undrafted" players would fit into this, since R seems to want to coerce the draft_year column as numerical to fit into a box plot.

Answer 1

From the ?cut help page, the breaks argument is:

breaks
either a numeric vector of two or more unique cut points or a single number (greater than or equal to 2) giving the number of intervals into which x is to be cut.

You gave it a single number, so that's interpreted as the number of intervals.

Instead, you should give it a vector of exact breakpoints, something like breaks = seq(1960, 2020, by = 5) .

I'm surprised you think your axis is being numericized--it's definitely a continuous axis, but I've never heard of ggplot doing that to a string or factor input--check your data frame to make sure the "Undrafted" rows are really there, they might have gotten dropped or converted to NA at some point. But that's a good thing for cut , because cut will only work on numerics. I'd suggest cutting the column as numeric to create a bin column, and then replace NA s in the bin column with "Undrafted" .

Answer 2

If you don't mind using a package, you can get the effect you want with:

library(santoku)

ggplot(..., aes(..., group = chop_width(draft_year, 5)))