Why?

June 8, 2017

UK R Courses

Filed under: R, Teaching — Tags: — csgillespie @ 8:30 am

Over the next few months we’re running a number of R, Stan and Scala courses around the UK.

June (London)
  • Mon Jun 26 – Introduction to R
  • Tue Jun 27 – Statistical Modelling with R
  • Wed Jun 28 – Programming with R
  • Thu Jun 29 (2-day course) – Advanced R Programming
August (Belfast)
  • Thu Aug 10 – Programming with R
  • Fri Aug 11 – Building an R Package
September 2017 (Newcastle)
  • Mon Sep 11 – Introduction to R
  • Tue Sep 12- Statistical Modelling with R
  • Wed Sep 13- Programming with R
  • Thu Sep 14- Advanced Graphics with R
  • Fri Sep 15- Automated Reporting (first steps towards Shiny)
  • Mon Sep 18 (5-day course) – Bioconductor
October (Glasgow)
  • Wed Oct 25 – Advanced Graphics with R
  • Thu Oct 26 (2-day course) – Advanced R Programming
November (London)
  • Mon Nov 06 (1-day course) – Efficient R Programming
  • Tue Nov 07 (1-day course) – R for Big Data
December (London/Newcastle)
  • Thu Dec 07 (2-day course) – Introduction to Bayesian Inference using RStan (Newcastle)
  • Mon Dec 11 (3-day course) – Scala for Statistical Computing and Data Science (London)

See the website for course descriptions. Any questions, feel free to contact me: colin@jumpingrivers.com

On site courses available on request.

June 7, 2017

Security: the dangers of copying and pasting R code

Filed under: Computing, R — Tags: — csgillespie @ 10:11 am

Most of the time when we stumble across a code snippet online, we often blindly copy and paste it into the R console. I suspect almost everyone does this. After all, what’s the harm? Consider this simple piece of R code that performs simple linear regression

# Generate data
x = rnorm(10)
y = rnorm(10)
message(“All your base are belong to us.”)
# Simple linear regression 
m = lm(y ~ x)

Now highlight the above piece of R code and copy and paste it into your console; look carefully at what you’ve pasted. A new line has magically appeared.

# Generate data
x = rnorm(10)
y = rnorm(10)
message("All your base are belong to us.")
# Simple linear regression
m = lm(y ~ x)

Due to some sneaky CSS magic, I was able to hide the message() statement. If I was evil, I could have changed this to a system, source, or any other command.

The CSS code simply sets the message() function to the background color, changes the font size and makes it un-selectable (see this post for details).

So remember, be careful with your copy and pasting!

January 25, 2017

Training courses: R, Stan and Scala

Filed under: R — Tags: , — csgillespie @ 1:34 pm

Over the next few months we’re running a number of R, Stan and Scala courses around the UK.

Feburary
  • Mon 13 – Introduction to R (London)
  • Tue 14 – Programming with R (London)
  • Wed 15 – Advanced Graphics with R (London)
  • Thur 16 (2-day course) – Predictive Analysis (London)
March
  • Tue Mar 21 – R for Big Data (Edinburgh)
  • Mon Mar 27 – Survival/Churn Analysis with R (London)
  • Tue Mar 28 – Building an R Package (London)
  • Wed Mar 29 – Automated Reporting (first steps towards Shiny) (London)
  • Thu Mar 30 – Interactive Graphics with Shiny (London)
  • Fri Mar 31 – Spatial Data Analysis with R (London)
April
  • Mon Apr 03 – Introduction to R (Newcastle)
  • Tue Apr 04 – Statistical Modelling with R (Newcastle)
  • Wed Apr 05 – Programming with R (Newcastle)
  • Thu Apr 06 – Efficient R Programming (Newcastle)
  • Fri Apr 07 – Advanced Graphics with R (Newcastle)
  • Mon Apr 10 (2-day course) – Introduction to Bayesian Inference using RStan (London)
May
  • Tue 16th (3-day course) – Scala for Statistical Computing and Data Science (London)
June
  • Thu Jun 08 (2-day course) – Advanced R Programming (Newcastle)
  • Mon Jun 26 – Introduction to R (London)
  • Tue Jun 27 – Statistical Modelling with R (London)
  • Wed Jun 28 – Programming with R (London)
  • Thu Jun 29 (2-day course) – Advanced R Programming (London)

See the website for course descriptions. Any questions, feel free to contact me: colin@jumpingrivers.com

On site courses available on request.

January 22, 2017

Input/output benchmarks

Filed under: Computing, R — Tags: — csgillespie @ 5:08 pm

To quantify the impact of the CPU on an analysis, I created the package benchmarkme. The idea is simple. If everyone runs the same R script, we can easily compare machines.

One of the benchmarks in the package is for comparing read/write speeds; we write a large CSV file (using write.csv) and read it back in using read.csv

The package is on CRAN can be installed in the usual way

install.packages("benchmarkme")

Running

library(benchmarkme)
## If your computer is relatively slow, remove 200 from below
res = benchmark_io(runs = 3, size = c(5, 50, 200))
## Upload you data set
upload_results(res)

creates three matrices of size 5MB, 20MB and 200MB, writes the associated CSV file to the directory

Sys.getenv("TMPDIR")

and then reads the data set back into R. The object res contains the timings which can compared to other users via

plot(res)

rplot01

The above graph plots the current benchmarking results for writing a 5MB file (my machine is relatively fast).

Shiny

You can also compare your results using the Shiny interface. Simply create a results bundle

 create_bundle(res, filename = "results.rds")

and upload to the webpage.

Network drives

Often the dataset we wish to access is on a network drive. Unfortunately, network drives can be slow. The benchmark_io function has an argument that allows us to change the directory and estimate the network drive impact

res_net = benchmark_io(runs = 3, size = c(5, 20, 200), 
                           tmpdir = "path_to_dir")

 

January 9, 2017

benchmarkme Update

Filed under: Computing, R — Tags: , — csgillespie @ 8:36 pm

When discussing how to speed up slow R code, my first question is what is your computer spec? It always surprises me when complex biological experiments, costing a significant amount of money, are analysed using a six year old laptop. A new desktop machine costs around £1000 and that money would be saved within a month in user time. Typically the more the RAM you have, the larger the dataset you can handle. However it’s not so obvious of the benefit of upgrading the processor.

To quantify the impact of the CPU on an analysis, I created the package benchmarkme. The aim of this package is to provide a set of benchmarks routines and data from past runs. You can then compare your machine, with other CPUs.

The package is now on CRAN and can be installed in the usual way

install.packages("benchmarkme")

The benchmark_std() function assesses numerical operations such as loops and matrix operations. This benchmark comprises of three separate benchmarks: prog, matrix_fun, and matrix_cal. If you have less than 3GB of RAM (run `get_ram()` to find out how much is available on your system), then you should kill any memory hungry applications, e.g. firefox, and set `runs = 1` as an argument.

To benchmark your system, use

library("benchmarkme")
res = benchmark_std(runs = 3)

You can compare your results to other users via

plot(res)


My laptop is ranked around 50 out of 300. However, relative to the fastest processor, there’s not much difference.

Finally upload your results for the benefit of other users

## You can control exactly what is uploaded. See details below.
upload_results(res)

Shiny

You can also compare your results using the Shiny interface. Simply create a results bundle

 create_bundle(res, filename = "results.rds")

and upload to the webpage.

What’s uploaded

Two objects are uploaded:

1. Your benchmarks from benchmark_std or benchmark_io;
2. A summary of your system information (get_sys_details()).

The get_sys_details() returns:

Sys.info();
get_platform_info();
get_r_version();
get_ram();
get_cpu();
get_byte_compiler();
get_linear_algebra();
installed.packages();
Sys.getlocale();
– The `benchmarkme` version number;
– Unique ID – used to extract results;
– The current date.

The function Sys.info() does include the user and nodenames. In the public release of the data, this information will be removed. If you don’t wish to upload certain information, just set the corresponding argument, i.e.

upload_results(res, args = list(sys_info=FALSE))

November 1, 2016

List of R conferences and useR groups

Filed under: Conferences, R — Tags: , — csgillespie @ 9:05 pm

Recently Steph Locke asked on twitter if there was a list of R conferences. After some googling, all that I came up was a list of useR groups maintained by Microsoft. While the list was lengthy, it was missing a few groups (and twitter handles). So the other night I created a github repository listing conferences/groups.

If you spot any missing groups or conferences, feel free to make a pull request at the GitHub Repository.

August 30, 2016

R Courses at London, Leeds and Newcastle

Filed under: R, Teaching — csgillespie @ 8:21 pm

Over the next few months we’re running a number of R courses at London, Leeds and Newcastle.

  • September 2016 (Newcastle)
    • Sept 12th: Introduction to R
    • Sept 13th: Statistical modelling
    • Sept 14th: Programming with R
    • Sept 15th: Efficient R: speeding up your code
    • Sept 16th: Advanced graphics
  • October 2016 (London)
    • Oct 3rd: Introduction to R
    • Oct 4th: Programming with R
    • Oct 5, 6th: Predictive analytics
    • Oct 7th: Building an R package
  • November 2016 (Leeds)
    • Nov 21st, 22nd: Predictive analytics
    • Nov 23rd: Building an R package
  • December 2016 (London)
    • December 5th, 6th: Advanced programming. Held at the Royal Statistical Society (booking form).
  • January 2017 (Newcastle)
    • Jan 16th: Introduction to R
    • Jan 17th: Statistical modelling
    • Jan 18th: Programming with R
    • Jan 19th: Efficient R: speeding up your code
    • Jan 20th: Advanced graphics

See the website for course description. Any questions, feel free to contact me: csgillespie@gmail.com

On site courses available on request.

April 22, 2016

R Courses at Newcastle

Filed under: Computing, R, Teaching — Tags: , — csgillespie @ 7:09 pm

Over the next two months I’m running a number of R courses at Newcastle University.

  • May 2016
    • May 10th, 11th: Predictive Analytics
    • May 16th – 20th: Bioconductor
    • May 23rd, 24th: Advanced programming
  • June 2016
    • June 8th: R for Big Data
    • June 9th: Interactive graphics with Shiny

Since these courses are on  advanced topics, numbers are limited (there’s only a couple of places left on Predictive Analytics). If you are interested in attending, sign up as soon as possible.

Getting to Newcastle is easy. The airport is 10 minutes from the city centre and has direct flights to the main airport hubs: Schiphol, Heathrow, and Paris.  The courses at Newcastle attract participants from around the world; at the April course, we had representatives from North America, Sweden, Germany,  Romania and Geneva.

Cost: The courses cost around £130 per day (more than half the price of certain London courses!)

 

Onsite courses available on request.

April 1, 2016

RStudio addins manager

Filed under: Computing, R — Tags: — csgillespie @ 12:36 am

RStudio addins let you execute a bit of R code or a Shiny app through the RStudio IDE, either via the Addins dropdown menu or with a keyboard shortcut. This package is an RStudio addin for managing other addins. To run these addins, you need the latest version of RStudio.

Installation

The package can be installed via devtools

## Need the latest version of DT as well
devtools::install_github('rstudio/DT')
devtools::install_github("csgillespie/addinmanager")

Running addins

After installing the package, the Addins menu toolbar will be populated with a new addin called Addin Manager. When you launch this addin, a DT table will be launched:

screenshot

In the screenshot above, the highlighted addins, shinyjs and ggThemeAssit, indicate that this addins have already installed.

When you click Done

  • Highlighted addins will be installed.
  • Un-highlighted addins will be removed.

Simple!

Including your addin

Just fork and alter the addin file which is located in the inst/extdata directory of the package. This file is a csv file with three columns:

  • addin Name/title
  • Brief Description
  • Package. If the package is only on github, use name/repo.

The initial list of addins was obtain from daattali’s repo.

February 16, 2016

RANDU: The case of the bad RNG

Filed under: Computing, R — Tags: , , — csgillespie @ 12:15 pm

The German Federal Office for Information Security (BSI) has established
criteria for quality random number generator (rng):

  • A sequence of random numbers has a high probability of containing no identical consecutive elements.
  • A sequence of numbers which is indistinguishable from true random’ numbers (tested using statistical tests.
  • It should be impossible to calculate, or guess, from any given sub-sequence, any previous or future values in the sequence.
  • It should be impossible, for all practical purposes, for an attacker to calculate, or guess the values used in the random number algorithm.

Points 3 and 4 are crucial for many applications. Everytime you make a
phone call, contact to a wireless point, pay using your credit card random
numbers are used.

Designing a good random number generator is hard and as a general rule you should never try to. R comes with many good quality random generators. The default generator is the Mersenne-Twister. This rng has a huge period of 2^{19937}-1 (how many random numbers are generated before we have a repeat).

Linear congruential generators

A linear congruential generator (lcg) is a relatively simple rng (popular in the 60’s and 70’s). It has a simple form of

r_{i}=(ar_{i-1}+b) \textrm{ mod }m, \quad i=1, 2, \ldots, m

where $latexr_0$ is the initial number, known as the seed, and \(a,b,m\) are the multiplier, additive constant and modulo respectively. The parameters are all integers.

The modulo operation means that at most m different numbers can be generated
before the sequence must repeat – namely the integers 0,1,2, \ldots, m-1. The
actual number of generated numbers is h \leq m, called the period of
the generator.

The key to random number generators is in setting the parameters.

RANDU

RANDU was a lcg with parameters m=2^{31}, a=65539 and b=0. Unfortunately this is a spectacularly bad choice of
parameters. On noting that a=65,539=2^{16}+3, then

r_{i+1} = a r_i = 65539 \times r_i = (2^{16}+3)r_i \;.

So

r_{i+2} = a\;r_{i+1} = (2^{16}+3) \times r_{i+1} = (2^{16}+3)^2 r_i \;.

On expanding the square, we get

r_{i+2} = (2^{32}+6\times 2^{16} + 9)r_i = [6 (2^{16}+3)-9]r_i = 6 r_{i+1} - 9 r_i \;.

Note: all these calculations should be to the mod 2^{31}. So there is a large
correlation between the three points!

If compare randu to a standard rng (code in a gist)

Rplot1

It’s obvious that randu doesn’t produce good random numbers. Plotting  x_i, x_{i-1} and x_{i-2} in 3d

Rplot2

Generating the graphics

The code is all in a gist and can be run via


devtools::source_gist("https://gist.github.com/csgillespie/0ba4bbd8da0d1264b124")

You can then get the 3d plot via


scatterplot3d::scatterplot3d(randu[,1], randu[,2], randu[,3],
angle=154)
## Interactive version
threejs::scatterplot3js(randu[,1], randu[,2], randu[,3])

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