Treemaps

Treemaps are somewhat controversial in data visualization circles. According to Tufte's commandments, data graphics must, among other things:

Show the data
Induce the viewer to think about substance rather than the methodology
Avoid distortion
Make large datasets coherent
Encourage the eye to compare different pieces of data
Reveal the data at several levels of detail

The question many arrive at with Treemaps are ... do they?

Let's explore.

If you haven't aleady, activate your dataviz environment and open Jupyter Notebooks. You'll need to run this command at the top:

install.packages('treemap', repos='http://cran.us.r-project.org')

If you get an error message: Close Jupyter, shut down the server in your terminal, and run this command: conda install r-essentials which will update all the libraries. I needed to do this on a Mac. PC worked.

For our example, we'll make a Treemap of our college enrollment data. The goal is to show which colleges are bigger than others, as well as the majors within them.



In [1]:

    
library(treemap)



In [2]:

    
enrollment <- read.csv("../../Data/collegeenrollment.csv")



In [3]:

    
head(enrollment)









    





College Degree MajorCode MajorName RaceGender Race Gender Count Total

	College of Agri Sci and Natl Resources B1BC                                  BIOC                                  Biochemistry                          NonResidentAlienMale                  NonResidentAlien                      Male                                  3                                      97                                   
	College of Agri Sci and Natl Resources B1AS                                  ASCI                                  Animal Science                        NonResidentAlienMale                  NonResidentAlien                      Male                                  0                                     338                                   
	College of Agri Sci and Natl Resources B1FW                                  FWL                                   Fisheries and Wildlife                NonResidentAlienMale                  NonResidentAlien                      Male                                  0                                     191                                   
	College of Agri Sci and Natl Resources B1AP                                  APSC                                  Applied Science                       NonResidentAlienMale                  NonResidentAlien                      Male                                  1                                      71                                   
	College of Agri Sci and Natl Resources B1HO                                  HORT                                  Horticulture                          NonResidentAlienMale                  NonResidentAlien                      Male                                  1                                      52                                   
	College of Agri Sci and Natl Resources B1ED                                  AEDU                                  Agricultural Education                NonResidentAlienMale                  NonResidentAlien                      Male                                  0                                     103



In [4]:

    
treemap(enrollment, 
    index=c("College","MajorName"),  # A list grouping variables: ORDER MATTERS.
    vSize = "Total",  # This determines the size, so it must be a number.
    title="Majors at UNL, 2017", # Customize the title
    fontsize.title = 24, #Change the font size of the title
    fontsize.labels=c(15,7), # Size of labels, must equal count of index
    fontcolor.labels=c("white","black"),     
    fontface.labels=c(2,1), # Font of labels: 1,2,3,4 for normal, bold, italic, bold-italic...
    bg.labels=c("transparent"), # Background color of labels
    align.labels=list(
        c("left", "top"), 
        c("right", "bottom")
        ), # Where to place labels in the rectangle?
    overlap.labels=0.5, # number between 0 and 1 that determines the overlap between labels.
    inflate.labels=F, # If true, labels are bigger when rectangle is bigger.
)

Discussion: Does this accomplish Tufte's commandments?

Show the data
Induce the viewer to think about substance rather than the methodology
Avoid distortion
Make large datasets coherent
Encourage the eye to compare different pieces of data
Reveal the data at several levels of detail

In class challenge: Make a treemap of UNL crime

Use dplyr to group by building and then by crime and count them up.
Make a treemap out of that dataframe.
Answer the question: Does it illuminate or distract?



In [ ]:

College	Degree	MajorCode	MajorName	RaceGender	Race	Gender	Count	Total
College of Agri Sci and Natl Resources	B1BC	BIOC	Biochemistry	NonResidentAlienMale	NonResidentAlien	Male	3	97
College of Agri Sci and Natl Resources	B1AS	ASCI	Animal Science	NonResidentAlienMale	NonResidentAlien	Male	0	338
College of Agri Sci and Natl Resources	B1FW	FWL	Fisheries and Wildlife	NonResidentAlienMale	NonResidentAlien	Male	0	191
College of Agri Sci and Natl Resources	B1AP	APSC	Applied Science	NonResidentAlienMale	NonResidentAlien	Male	1	71
College of Agri Sci and Natl Resources	B1HO	HORT	Horticulture	NonResidentAlienMale	NonResidentAlien	Male	1	52
College of Agri Sci and Natl Resources	B1ED	AEDU	Agricultural Education	NonResidentAlienMale	NonResidentAlien	Male	0	103