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Building a JSON webservice in R

R is a programming language for mathematics and statistics. There are several R libraries available to support web development, including rjson and RJSONIO (note case – R library names are case sensitive). RJSONIO is based on rjson, but with modifications to improve performance working with large JSON payloads. The example below returns the data required […]

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Unit testing in R

Commentary R is a statistical programming language, with a strong focus on mathematical operations. When writing code that is math-heavy, unit testing becomes very appealing- while equations may look correct on paper, one minor error can ruin the output. R programming is also different to CRUD or enterprise software in that the R in-memory data […]

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Building a statistical significance testing web service powered by R

R is a programming language focused on solving statistical and mathematical calculations. R programs often operate on large, in-memory data sets, which feels somewhat similar to database programming. Examples in the R Cookbook bear a resemblence to functional programming in clojure, as others have noted. I’ve been exploring the language to gain insight into related, […]

R Error: “Error in readBin(fileR, “integer”, n = Length/2, size = 2, signed = TRUE, : invalid ‘n’ argument”

The following error is an indication that an exceptional I/O error occurred. For instance, permissions denied, out of memory, etc. Normally the syntax of this error would indicate that a required parameter is missing from a function call, but with readBin it appears to be more often an exception. Error in readBin(fileR, “integer”, n = […]

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Marking time in R

In a previous example, I showed how to find the onset of a single drumbeat, as well as the chord at an instant. This new example extends the method to detect the onset of several notes in a row, and demonstrates some interesting challenges involved in musical transcription. The general process is to read in […]

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Finding the beat in R

In a previous article, I described a method for detecting chords in an audio file (also available for Scala). Continuing on this theme, the following will find the onset of a drumbeat in a file, using R. I’m using a single drumstick click, which you can hear on freesound.org. This method detects sudden volume increases- […]

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Book Review: R Cookbook

The R Cookbook is written by Paul Teetor, a developer with degrees in statistics and computer science, specializing in finance. The programming language R is a specialized language designed for deep statistical research, although it has some support for other mathematical fields, such as matrix algebra and signal processing. True to the O’Reilly cookbook format, […]

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Detecting Pitches in music with R

In a previous post, I described a method to detect a chord using a Fourier transform in Java/Scala. I’ve re-implemented the same in R, detailed below. This will generate an audio file containing the C-Major chord: library(sound) c<-261.63 e<-164.81 g<-196 len<-1 cData<-Sine(c,len) eData<-Sine(e,len) gData<-Sine(g,len) audio<-normalize(cData+eData+gData) saveSample(audio, “out\\ceg.wav”, overwrite=TRUE) And a series of helper functions: magnitude<-function(x) […]