Less Volume, More Creativity – Getting Started with the mosaic Package

Project MOSAIC and the mosaic package

NSF-funded project to develop a new way to introduce mathematics, statistics, computation and modeling to students in colleges and universities.

• more information at mosaic-web.org

• the mosaic package is available via
  • CRAN
  • github
    • updates more frequently than CRAN
    • use devtools::install_github(ProjectMOSAIC/mosaic) to install directly from github
    • add the optional ref="beta" to install from the beta (developmental) branch
    • add build_vignettes=TRUE if your system is equipped to build vignettes.

A note about this document

This document was originally created as an R presentation to be used as slides accompanying various presentations. It has been converted into a more traditional document for use as a vignette in the mosaic package.

The examples below use the mosaic and mosaicData packages.

require(mosaic)
require(mosaicData)

Less Volume, More Creativity

Many of the guiding principles of the mosaic package reflect the “Less Volume, More Creativity” mantra of Mike McCarthy who had a large poster with those words placed in the “war room” (where assistant coaches decide on the game plan for the upcoming opponent) as a constant reminder not to add too much complexity to the game plan.

A lot of times you end up putting in a lot more volume, because you are teaching fundamentals and you are teaching concepts that you need to put in, but you may not necessarily use because they are building blocks for other concepts and variations that will come off of that … In the offseason you have a chance to take a step back and tailor it more specifically towards your team and towards your players." Mike McCarthy, Head Coach, Green Bay Packers

SIBKIS: See It Big, Keep It Simple

Here is another elegant phrasing of a similar principle.

Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away. — Antoine de Saint-Exupery (writer, poet, pioneering aviator)

Less Volume, More Creativity in R

One key to successfully introducing R is finding a set of commands that is

• small: fewer is better
• coherent: commands should be as similar as possible
• powerful: can do what needs doing

It is not enough to use R, it must be used elegantly.

Two examples of this principle: * the mosaic package * the dplyr package (Hadley Wickham)

Minimal R

Goal: a minimal set of R commands for Intro Stats

Result: Minimal R Vignette (vignette("MinimalR"))

Much of the work on the mosaic package has been motivated by

• The Less Volume, More Creativity approach
• The Minimal R goal

A few little details

If you (or your students) are just getting started with R, it is good to keep the following in mind:

R is case sensitive

• many students are not case sensitive

Arrows and Tab

• up/down arrows scroll through history
• TAB completion can simplify typing

If all else fails, try ESC

• If you see a + prompt, it means R is waiting for more input
• If this is unintentional, you probably have a typo
• ESC will get you pack to the command prompt

The Most Important Template

 

The following template is important because we can do so much with it.

 

goal ( yyy ~ xxx , data = mydata )

 

It is useful to name the components of the template:

 

goal (  y  ~  x  , data = mydata )

  We’re hiding a bit of complexity in the template, and there will be times that we will want to gussy things up a bit. We’ll indicate that by adding ... to the end of the template. Just don’t let ... become a distractor early on.

 

goal (  y  ~  x  , data = mydata , …)

 

Other versions

Here are some variations on the template.

# simpler version
goal( ~ x, data = mydata )          
# fancier version
goal( y ~ x | z , data = mydata )   
# unified version
goal( formula , data = mydata )     

2 Questions

Using the template generally requires answering two questions. (These questions are useful in the context of nearly all computer tools, just substitute “the computer” in for R in the questions.)

 

goal (  y  ~  x  , data = mydata )

 

What do you want R to do? (goal)

• This determines the R function to use

What must R know to do that?

• This determines the inputs to the function
• Must identify the variables and data frame

How do we make this plot? (Questions)

What is the Goal?

What does R need to know?

How do we make this plot? (Answers)

What is the Goal?

• a scatter plot (xyplot())

What does R need to know?

• which variable goes where (births ~ date)
• which data set (data=Births78)
  • use ?Births78 for documentation

Putting it all together

xyplot( births ~ date, data=Births78) 

Your turn: How do you make this plot?