Blog Archives

Extracting Specific Lines from a Large (Compressed) Text File

May 26, 2018
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A few days ago a friend asked me the following question: how to efficiently extract some specific lines from a large text file, possibily compressed by Gzip? He mentioned that he tried some R functions such as read.table(skip = ...), but found that rea...

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Creating Pretty Documents with the prettydoc Package

August 10, 2016
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Creating Pretty Documents with the prettydoc Package

Have you ever tried to find a lightweight yet nice theme for the R Markdown documents, like this page? Themes for R Markdown With the powerful rmarkdown package, we could easily create nice HTML document by adding some meta information in the header, for example --- title: Nineteen Years Later author: Harry Potter date: July 31, 2016 output: rmarkdown::html_document: theme: lumen --- The html_document engine uses the Bootswatch theme...

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recosystem: Recommender System Using Parallel Matrix Factorization

July 14, 2016
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recosystem: Recommender System Using Parallel Matrix Factorization

A Quick View of Recommender System The main task of recommender system is to predict unknown entries in the rating matrix based on observed values, as is shown in the table below: Each cell with number in it is the rating given by some user on a specific item, while those marked with question marks are unknown ratings that need to be...

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RcppNumerical: Numerical integration and optimization with Rcpp

April 8, 2016
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Introduction I have seen several conversations in Rcpp-devel mailing list asking how to compute numerical integration or optimization in Rcpp. While R in fact has the functions Rdqags, Rdqagi, nmmin, vmmin etc. in its API to accomplish such tasks, it i...

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Large scale eigenvalue decomposition and SVD with rARPACK

February 19, 2016
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In January 2016, I was honored to receive an “Honorable Mention” of the John Chambers Award 2016. This article was written for R-bloggers, whose builder, Tal Galili, kindly invited me to write an introduction to the rARPACK package. A Short Story of rARPACK Eigenvalue decomposition is a commonly used technique in numerous statistical problems. For example, principal component analysis...

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