Posted on Categories Administrativia, Opinion, Practical Data Science, StatisticsTags , , 2 Comments on Practical Data Science with R update

Practical Data Science with R update

Just got the following note from a new reader:

Thank you for writing Practical Data Science with R. It’s challenging for me, but I am learning a lot by following your steps and entering the commands.

Wow, this is exactly what Nina Zumel and I hoped for. We wish we could make everything easy, but an appropriate amount of challenge is required for significant learning and accomplishment.

Of course we try to avoid inessential problems. All of the code examples from the book can be found here (and all the data sets here).

The second edition is coming out very soon. Please check it out.

Posted on Categories data science, Practical Data Science, Pragmatic Data Science, Pragmatic Machine Learning, Statistics, TutorialsTags , , , Leave a comment on WVPlots 1.1.2 on CRAN

WVPlots 1.1.2 on CRAN

I have put a new release of the WVPlots package up on CRAN. This release adds palette and/or color controls to most of the plotting functions in the package.

WVPlots was originally a catch-all package of ggplot2 visualizations that we at Win-Vector tended to use repeatedly, and wanted to turn into “one-liners.” A consequence of this is that the older visualizations had our preferred color schemes hard-coded in. More recent additions to the package sometimes had palette or color controls, but not in a consistent way. Making color controls more consistent has been a “todo” for a while—one that I’d been putting off. A recent request from user Brice Richard (thanks Brice!) has pushed me to finally make the changes.

Most visualizations in the package that color-code by group now have a palette argument that takes the name of a Brewer palette for the graph; Dark2 is usually the default. To use the ggplot2 default palette, or to set an alternative palette, such as viridis or a manually specified color scheme, set palette=NULL. Here’s some examples:

library(WVPlots)
library(ggplot2)

mpg = ggplot2::mpg
mpg$trans = gsub("\\(.*$", '', mpg$trans)
 
# default palette: Dark2 
DoubleDensityPlot(mpg, "cty", "trans", "City driving mpg by transmission type")

Unnamed chunk 1 1

# set a different Brewer color palette
DoubleDensityPlot(mpg, "cty", "trans", 
                  "City driving mpg by transmission type",
                  palette = "Accent")

Unnamed chunk 1 2

# set a custom palette
cmap = c("auto" = "#7b3294", "manual" = "#008837")

DoubleDensityPlot(mpg, "cty", "trans", 
                  "City driving mpg by transmission type",
                  palette=NULL) + 
  scale_color_manual(values=cmap) + 
  scale_fill_manual(values=cmap)

Unnamed chunk 1 3

For other plots, the user can now specify the desired color for different elements of the graph.

title = "Count of cars by number of carburetors and cylinders"

# default fill: darkblue
ShadowPlot(mtcars, "carb", "cyl",
           title = title)

Unnamed chunk 2 1

# specify fill
ShadowPlot(mtcars, "carb", "cyl",
           title = title,
           fillcolor = "#a6611a")

Unnamed chunk 2 2

We hope that these changes make WVPlots even more useful to our users. For examples of several of the visualizations in WVPlots, see this example vignette. For the complete list of visualizations, see the reference page.

Posted on Categories data science, Opinion, Pragmatic Data Science, Pragmatic Machine Learning, TutorialsTags , , , , , , , , Leave a comment on Advanced Data Reshaping in Python and R

Advanced Data Reshaping in Python and R

This note is a simple data wrangling example worked using both the Python data_algebra package and the R cdata package. Both of these packages make data wrangling easy through he use of coordinatized data concepts (relying heavily on Codd’s “rule of access”).

The advantages of data_algebra and cdata are:

  • The user specifies their desired transform declaratively by example and in data. What one does is: work an example, and then write down what you want (we have a tutorial on this here).
  • The transform systems can print what a transform is going to do. This makes reasoning about data transforms much easier.
  • The transforms, as they themselves are written as data, can be easily shared between systems (such as R and Python).

Continue reading Advanced Data Reshaping in Python and R

Posted on Categories Administrativia, Opinion, Pragmatic Data Science, Pragmatic Machine Learning, TutorialsTags , Leave a comment on New Getting Started with vtreat Documentation

New Getting Started with vtreat Documentation

Win Vector LLC‘s Dr. Nina Zumel has just released some new vtreat documentation.

vtreat is a an all-in one step data preparation system that helps defend your machine learning algorithms from:

  • Missing values
  • Large cardinality categorical variables
  • Novel levels from categorical variables

I hoped she could get the Python vtreat documentation up to parity with the R vtreat documentation. But I think she really hit the ball out of the park, and went way past that.

The new documentation is 3 “getting started” guides. These guides deliberately overlap, so you don’t have to read them all. Just read the one suited to your problem and go.

The new guides:

Perhaps we can back-port the new guides to the R version at some point.

Posted on Categories Administrativia, OpinionTags , Leave a comment on Why R?

Why R?

I was working with our copy editor on Appendix A of Practical Data Science with R, 2nd Edition; Zumel, Mount; Manning 2019, and ran into this little point (unfortunately) buried in the back of the book.

In our opinion the R ecosystem is the fastest path to substantial data science, statistical, and machine learning accomplishment.

This is why we use and teach R (in addition to using and teaching Python).

Posted on Categories Opinion, RantsTags , 9 Comments on It is Time for CRAN to Ban Package Ads

It is Time for CRAN to Ban Package Ads

NPM (a popular Javascript package repository) just banned package advertisements. I feel the CRAN repository should do the same.

Continue reading It is Time for CRAN to Ban Package Ads

Posted on Categories Administrativia, data science, Opinion, Pragmatic Data Science, Pragmatic Machine Learning, TutorialsTags , , , , , , , , Leave a comment on Introducing data_algebra

Introducing data_algebra

This article introduces the data_algebra project: a data processing tool family available in R and Python. These tools are designed to transform data either in-memory or on remote databases.

In particular we will discuss the Python implementation (also called data_algebra) and its relation to the mature R implementations (rquery and rqdatatable).

Continue reading Introducing data_algebra

Posted on Categories Computer Science, Programming, TutorialsTags , , Leave a comment on Eliminating Tail Calls in Python Using Exceptions

Eliminating Tail Calls in Python Using Exceptions

I was working through Kyle Miller‘s excellent note: “Tail call recursion in Python”, and decided to experiment with variations of the techniques.

The idea is: one may want to eliminate use of the Python language call-stack in the case of a “tail calls” (a function call where the result is not used by the calling function, but instead immediately returned). Tail call elimination can both speed up programs, and cut down on the overhead of maintaining intermediate stack frames and environments that will never be used again.

The note correctly points out that Python purposely does not have a goto statement, a tool one might use to implement true tail call elimination. So Kyle Miller built up a data-structure based replacement for the call stack, which allows one to work around the stack-limit for a specific function (without changing any Python configuration, and without changing the behavior of other functions).

Of course Python does have some exotic control-flow controls: raise and yield. So I decided to build an exception based solution of our own using raise .

Please read on for how we do this, and for some examples.

Continue reading Eliminating Tail Calls in Python Using Exceptions

Posted on Categories Pragmatic Data Science, Pragmatic Machine Learning, TutorialsTags , , , , , Leave a comment on What is vtreat?

What is vtreat?

vtreat is a DataFrame processor/conditioner that prepares real-world data for supervised machine learning or predictive modeling in a statistically sound manner.

vtreat takes an input DataFrame that has a specified column called “the outcome variable” (or “y”) that is the quantity to be predicted (and must not have missing values). Other input columns are possible explanatory variables (typically numeric or categorical/string-valued, these columns may have missing values) that the user later wants to use to predict “y”. In practice such an input DataFrame may not be immediately suitable for machine learning procedures that often expect only numeric explanatory variables, and may not tolerate missing values.

To solve this, vtreat builds a transformed DataFrame where all explanatory variable columns have been transformed into a number of numeric explanatory variable columns, without missing values. The vtreat implementation produces derived numeric columns that capture most of the information relating the explanatory columns to the specified “y” or dependent/outcome column through a number of numeric transforms (indicator variables, impact codes, prevalence codes, and more). This transformed DataFrame is suitable for a wide range of supervised learning methods from linear regression, through gradient boosted machines.

The idea is: you can take a DataFrame of messy real world data and easily, faithfully, reliably, and repeatably prepare it for machine learning using documented methods using vtreat. Incorporating vtreat into your machine learning workflow lets you quickly work with very diverse structured data.

Worked examples can be found here.

For more detail please see here: arXiv:1611.09477 stat.AP (the documentation describes the R version, however all of the examples can be found worked in Python here).

vtreat is available as a Python/Pandas package, and also as an R package.

(logo: Julie Mount, source: “The Harvest” by Boris Kustodiev 1914)

Some operational examples can be found here.

Posted on Categories Administrativia, Pragmatic Data ScienceTags , , , , Leave a comment on Speaking at BARUG

Speaking at BARUG

We will be speaking at the Tuesday, September 3, 2019 BARUG. If you are in the Bay Area, please come see us.

Nina Zumel & John Mount
Practical Data Science with R

Practical Data Science with R (Zumel and Mount) was one of the first, and most widely-read books on the practice of doing Data Science using R. We have been working hard on an improved and revised 2nd edition of our book (coming out this Fall). The book reflects more experience with data science, teaching, and with R itself. We will talk about what direction we think the R community has been taking, how this affected the book, and what is new in the upcoming edition.