# Articles by csgillespie

### Survival paper (update)

January 13, 2011 |

In a recent post, I discussed some  statistical consultancy I was involved with. I was quite proud of the nice ggplot2 graphics I had created. The graphs nicely summarised the main points of the paper: I’ve just had the proofs from the journal, and next to the graphs there ...
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### Random variable generation (Pt 3 of 3)

January 12, 2011 |

Ratio-of-uniforms This post is based on chapter 1.4.3 of Advanced Markov Chain Monte Carlo.  Previous posts on this book can be found via the  AMCMC tag. The ratio-of-uniforms was initially developed by Kinderman and Monahan (1977) and can be used for generating random numbers from many standard distributions. Essentially we transform the ... [Read more...]

### R programming books

December 21, 2010 |

My sabbatical is rapidly coming to an end, and I have to start thinking more and more about teaching. Glancing over my module description for the introductory computational statistics course I teach, I noticed that it’s a bit light on recommend/background reading. In fact it has only two ... [Read more...]

### Logical operators in R

December 14, 2010 |

In R, the operators “|” and “&” indicate the logical operations OR and AND. For example, to test if x equals 1 and y equals 2 we do the following: __ x = 1; y = 2 __ (x == 1) & (y == 2) [1] TRUE However, if you are used to programming in [...] [Read more...]

### New paper: Survival analysis

December 8, 2010 |

Each year I try to carry out some statistical consultancy to give me experience in other areas of statistics and also to provide teaching examples. Last Christmas I was approached by a paediatric consultant from the RVI who wanted to carry out prospective survival analysis. The consultant, Bruce  Jaffray, had ... [Read more...]

### Random variable generation (Pt 2 of 3)

December 2, 2010 |

Acceptance-rejection methods This post is based on chapter 1.4 of Advanced Markov Chain Monte Carlo. Another method of generating random variates from distributions is to use acceptance-rejection methods. Basically to generate a random number from , we generate a RN from an envelope distribution , where .  The acceptance-rejection algorithm is as follows: Repeat ... [Read more...]

### Random variable generation (Pt 1 of 3)

November 28, 2010 |

As I mentioned in a recent post, I’ve just received a copy of Advanced Markov Chain Monte Carlo Methods. Chapter 1.4 in the book (very quickly) covers random variable generation. Inverse CDF Method A standard algorithm for generating random numbers is the inverse cdf method. The continuous version of the ... [Read more...]

### Advanced Markov Chain Monte Carlo Methods (AMCMC)

November 27, 2010 |

I’ve just received my copy of Advanced Markov Chain Monte Carlo Methods, by Liang, Liu, & Carroll. Although my PhD didn’t really involve any Bayesian methodology (and my undergrad was devoid of any Bayesian influence), I’ve found that the sort of problems I’m now tackling in systems ... [Read more...]

### R Style Guide

November 23, 2010 |

Each year I have the pleasure (actually it’s quite fun) of teaching R programming to first year mathematics and statistics students. The vast majority of these students have no experience of programming, yet think they are good with computers because they use facebook! The class has around 100 students, and ... [Read more...]

### Assignment operators in R: ‘=’ vs. ‘<-’

November 16, 2010 |

In R, you can use  both ‘=’ and ‘ rm(x) __ mean(x=1:10) [...] [Read more...]

### Installing R packages

November 6, 2010 |

Part of the reason R has become so popular is the vast array of packages available at the cran and bioconductor repositories. In the last few years, the number of packages has grown exponentially! This is a short post giving steps on how to actually install R packages. Let’s ... [Read more...]

### An analysis of the Stackoverflow Beta sites

November 1, 2010 |

In the last six months or so, the behemoth of Q & A sites stackoverflow, decided to change tack and launch a number of other non-computing-language sites. To launch a site in the stackoverflow family, sites have to spend time gathering followers in Area51. Once a site has gained a critical ... [Read more...]
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