Blog Archives

Heteroscedasticity in Regression — It Matters!

June 7, 2015
By
Heteroscedasticity in Regression — It Matters!

R’s main linear and nonlinear regression functions, lm() and nls(), report standard errors for parameter estimates under the assumption of homoscedasticity, a fancy word for a situation that rarely occurs in practice. The assumption is that the (conditional) variance of the response variable is the same at any set of values of the predictor variables. … Continue reading...

Read more »

Macros in R

June 5, 2015
By
Macros in R

In programming, sometimes it’s useful to write a macro rather than a function. (Don’t worry if you’ve never heard the term before.) In this post, I’ll give an example of use of macros in R. using the gtools package on CRAN. I wanted to write some utility code to help me reuse my earlier R commands during … Continue reading...

Read more »

Discovered Two Great Web Sites Today

June 3, 2015
By
Discovered Two Great Web Sites Today

Today is my lucky day.  I learned of two very interesting Web pages, both of them quite informative and the first of them rather provocative (yay!). I have some comments on both, in some cases consisting of mild disagreement, which I may post later, but in any event, I highly recommend both.  Here they are: … Continue reading...

Read more »

Update on Snowdoop, a MapReduce Alternative

May 29, 2015
By
Update on Snowdoop, a MapReduce Alternative

In blog posts a few months ago, I proposed an alternative to MapReduce, e.g. to Hadoop, which I called “Snowdoop.” I pointed out that systems like Hadoop and Spark are very difficult to install and configure, are either too primitive (Hadoop)  or too abstract (Spark) to program, and above all, are SLOW. Spark is of … Continue reading...

Read more »

My New Book and Other Matters

May 22, 2015
By
My New Book and Other Matters

I haven’t posted for a while, so here are some news items: My new book, Parallel Computation for Data Science, will be out in June or July. I believe it will be useful to anyone doing computationally intensive work. After a few months being busy with the book and other things, I have returned to … Continue reading...

Read more »

Tutorial on High-Performance Computing in R

February 3, 2015
By
Tutorial on High-Performance Computing in R

I wanted to call your attention to what promises to be an outstanding tutorial on High-Performance Computing (HPC) in R, presented in Web streaming format. My Rth package coauthor Drew Schmidt, who is also one of the authors of the pbdR package, will be one of the presenters.  Should very interesting and useful.

Read more »

GPU Tutorial, with R Interfacing

January 24, 2015
By
GPU Tutorial, with R Interfacing

You’ve heard that graphics processing units — GPUs — can bring big increases in computational speed.  While GPUs cannot speed up work in every application, the fact is that in many cases it can indeed provide very rapid computation.  In this tutorial, we’ll see how this is done, both in passive ways (you write only … Continue reading...

Read more »

OpenMP Tutorial, with R Interface

January 17, 2015
By
OpenMP Tutorial, with R Interface

Almost any PC today is multicore.  Dual-core is standard, quad-core is easily attainable for the home, and larger systems, say 16-core, are easily within reach of even smaller research projects. In addition, large multicore systems can be “rented” on Amazon EC2 and so on. The most popular way to program on multicore machines is to … Continue reading...

Read more »

Debugging Parallel Code with dbs()

January 4, 2015
By
Debugging Parallel Code with dbs()

I mentioned yesterday that my partools package is now on CRAN.  A number of people have expressed interest in the Snowdoop section, but in this post I want to call attention to the dbs() debugging tool in the package, useful for debugging code written for the portion of R’s parallel library that came from the … Continue reading...

Read more »

Snowdoop/partools Package Now on CRAN

January 3, 2015
By
Snowdoop/partools Package Now on CRAN

I’ve now placed the partools package, including Snowdoop, on CRAN.  No major new functions since my last posting, but the existing functions have been made more versatile and convenient, and the documentation is now more detailed, with more examples and so on.  I do have more functions planned. It is all platform independent, except for … Continue reading...

Read more »