Monthly Archives: September 2011

An example of ROC curves plotting with ROCR

September 3, 2011
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An example of ROC curves plotting with ROCR

Decided to start githib with ROC curve plotting example. There is not a one ROC curve but several - according to the number of comparisons (classifications), also legend with maximal and minimal ROC AUC are added to the plot. ROC curves and ROC AU...

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rmongodb – R Driver for MongoDB

September 3, 2011
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The source code to rmongodb (home page at http://cnub.org/rmongodb.ashx), a driver to MongoDB for the R language, has been released as open source at GitHub: https://github.com/gerald-lindsly/rmongodb.  This portable full-featured package was developed on top of the mongodb.org supported C driver. It runs almost entirely in native code so you can expect high performance.  Plans are to submit rmongodb to CRAN soon for pre-built binary distribution, but first I would...

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A quick way to do row repeat and col repeat (rep.row, rep.col)

September 2, 2011
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A quick way to do row repeat and col repeat (rep.row, rep.col)

Today I worked on a simulation program which require me to create a matrix by repeating the vector n times (both by row and by col). Even the task is extremely simple and only take 1 line to finish(10sec), I have to think about should the argument in rep be each or times and should

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Discussion thread on R vs SAS for businesses

September 2, 2011
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There's an interesting discussion thread on LinkedIn going on now on the relative benefits of R versus SAS in the commercial sector. Oleg Okun kicks off the discussion with this question: Did anyone have to justify to a prospect/customer why R is better than SAS? What arguments did you provide? Did your prospect/customer agree with them? Why do you...

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Assessing the Forecasting Ability of Our Model

September 2, 2011
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Assessing the Forecasting Ability of Our Model

Today we wish to see how our model would have faired forecasting the past 20 values of GDP. Why? Well ask yourself this: How can you know where your going, if you don't know where you've been? Once you understand please proceed on with the following post.First recall the trend portion that we have already accounted for:> t=(1:258)> t2=t^2> trendy= 892.656210 +...

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Part 2 of 3: Non-linear Optimization of Predictive Models with R

September 2, 2011
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In my previous post, I was able to build a predictive model (simple linear model) to predict the gross margin % of an eCommerce site based on the promotional spend accross various paid channels.  I repeated the process for AOV (average order ...

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Using Google Spreadsheets as a Database Source for R

September 2, 2011
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Using Google Spreadsheets as a Database Source for R

I couldn’t contain myself (other more pressing things to do, but…), so I just took a quick time out and a coffee to put together a quick and dirty R function that will let me run queries over Google spreadsheet data sources and essentially treat them as database tables (e.g. Using Google Spreadsheets as a

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Word Cloud from Blog RSS

September 2, 2011
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Word Cloud from Blog RSS

Crazy busy  - no time to blog recently. Time enough for pretty pictures based upon previous words though...(thanks http://www.wordle.net).

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Fix missing dates with R

September 2, 2011
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Fix missing dates with R

I have data on user access to a website. This log file (helpdesk log.csv) just contains the date of access, and how many accesses were counted. It would look like this:Date hits13-07-2011 214-07-2011 116-07-2011 317-07-2011 4...As you can see, for day...

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Density curve of histogram plot in R

September 1, 2011
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Density curve of histogram plot in R

Ref: http://casoilresource.lawr.ucdavis.edu/drupal/book/export/html/23 To add density curve on a histogram, like the green curve above, use code below:#plot the distributionhist(slope, breaks=1000, freq=F, main=main, xlab="Slope Value (percent)", ...

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