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Category: R

Preparing Text Data For Natural Language Processing

Shirin Glander takes us through the process of preparing natural language data for machine learning using Keras:

As with any neural network, we need to convert our data into a numeric format; in Keras and TensorFlow we work with tensors. The IMDB example data from the keras package has been preprocessed to a list of integers, where every integer corresponds to a word arranged by descending word frequency.

So, how do we make it from raw text to such a list of integers? Luckily, Keras offers a few convenience functions that make our lives much easier.

This is a very nice tutorial if you’re new to the process.

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UTF-8 And R

Sebastian Sauer gives us a brief overview of UTF-8 support in R and other relevant tools (like Excel):

That seems to work easily. Maybe that’s the easiest way at the end of the day (?).

One problem that may arise – besides building on proprietary code that may change without notice – is that Excel may have problems reading a UTF8 csv, as explained here.

Read on for more info on what has become the de facto web standard for text.

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Analytical Pipelines In R With H2O And AWS

Hanjo Oden wraps up a series on training models on AWS using H2O in R:

To generate these, you can log into your AWS dashboard, go to the IAM (Identity and Access Management) dashboard and select the Users tab. On the Userstab, add a user and also the administration rights that you want the user to have.Remember to restart R once you have filled in the access key information in the .Renviron file for it to take effect.

At this point, those familiar with cloudyr suite is probably asking – “This is exactly the same as library(aws.ec2), so why use boto3?“. Well, to be honest, I was using aws.ec2 for a while, but I find spot-instances, which the current version of aws.ec2 does not support. In addition I found that boto3 has some other functionalitue – which I prefer. For a full list of boto3 functions to interact with an EC2 instance, have a look at the reference manual.

It’s pretty good stuff; check it out.

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Genetic Algorithms In R

Pablo Casas touches on one of my favorite lost causes:

In machine learning, one of the uses of genetic algorithms is to pick up the right number of variables in order to create a predictive model.

To pick up the right subset of variables is a problem of combinatory logic and optimization.

The advantage of this technique over others is that it allows the best solution to emerge from the best of the prior solutions. An evolutionary algorithm which improves the selection over time.

The idea of GA is to combine the different solutions generation after generation to extract the best genes (variables) from each one. That way it creates new and more fit individuals.

We can find other uses of GA such as hyper-tunning parameters, finding the maximum (or minimum) of a function, or searching for the correct neural network architecture (neuroevolution), among others.

I’ve seen a few people use genetic algorithms in the past decade, but usually for hyperparameter tuning rather than as a primary algorithm. It was always the “algorithm of last resort” even before neural networks took over the industry, but if you want to spend way too much time on the topic, I have a series. If you have too much time on your hands and meet me in person, ask about my thesis.

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Running RStudio Server In Azure

David Smith notes that RStudio Server Pro is now available on Azure:

RStudio Server Pro is now available on the Azure Marketplace, the company announced on the RStudio Blog earlier this month. This means you can launch RStudio Server Pro on an virtual machine with the memory, disk, and CPU configuration of your choice, and pay by the minute for the VM instance plus a the RStudio software charge. Then, you can use a browser to access the remote RStudio Server (the interface is nigh-indistinguishable from the desktop version), with access to the commercial features of RStudio including support for multiple R version and concurrent R sessions, load-balancing and high availability instances, and enhanced security.

RStudio Server Pro and Microsoft R Server are both very nice for production-quality R servers. You can get away with the open source versions, but there are some good reasons to use the enterprise-grade products in an enterprise.

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Using Plotly In Power BI

Kara Annanie shows how you can R integration in Power BI to push Plotly visuals to users:

In the example, above, we’ve created a line chart visualization using Plotly and we’ve decided to put labels on the graph, but only on the first and last points of the line graph. This graph would be particularly useful to show 13 months of data overtime, where the left-most label shows January of last year, for example, and the right-most label shows January of this year, for example. The user could still view the trend across the year between both January data points.

Click through for a pair of videos and some notes on how to get started.

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Inline Operators In R With wrapr

John Mount shows how to use inline operators in R with the wrapr package:

The above code is assuming you have the wrapr package attached via already having run library('wrapr').

Notice we picked R-related operator names. We stayed away from overloading the + operator, as the arithmetic operators are somewhat special in how they dispatch in R. The goal wasn’t to make R more like Python, but to adapt a good idea from Python to improve R.

Also, it’s a little late to pick up the discount (though Manning has discounts pretty much every day so be patient and you’ll find 40+ percent off) but check out the second edition of Practical Data Science with R by Mount and Nina Zumel. I’ve held off on reading it so far because I want to wait until it’s closer to completion, but it is on my to-read list.

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Feature And Text Classification Using Naive Bayes In R

I wrap up my series on the Naive Bayes class of algorithms, finally writing some code along the way:

Now we’re going to look at movie reviews and predict whether a movie review is a positive or a negative review based on its words. If you want to play along at home, grab the data set, which is under 3MB zipped in 2000 reviews in total.

Unike last time, I’m going to break this out into sections with commentary in between. If you want the full script with notebook, check out the GitHub repo I put together for this talk.

Assuming I ever get a chance to do this talk again, I’m probably going to change the data sets in the example given how overplayed iris is.

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An Explanation Of Convolutional Neural Networks

Shirin Glander explains some of the mechanics behind Convolutional Neural Networks:

Convolutional Neural Nets are usually abbreviated either CNNs or ConvNets. They are a specific type of neural network that has very particular differences compared to MLPs. Basically, you can think of CNNs as working similarly to the receptive fields of photoreceptors in the human eye. Receptive fields in our eyes are small connected areas on the retina where groups of many photo-receptors stimulate much fewer ganglion cells. Thus, each ganglion cell can be stimulated by a large number of receptors, so that a complex input is condensed into a compressed output before it is further processed in the brain.

If you’re interested in understanding why a CNN will classify the way it does, chapter 5 of Deep Learning with R is a great reference.

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Getting CSV Row Counts

Dave Mason shares a few techniques for getting row counts of CSV files:

I was reminded of this recently as I was working with R, trying to read a nearly 2 GB data file. I wanted to read in 5% of the data and output it to a smaller file that would make the test code run faster. The particular function I was working with needed a row count as one of its parameters. For me, that meant I had to determine the number of rows in the source file and multiply by 0.05. I tied the code for all of those tasks into one script block.
Now, none to my surprise, it was slow. In my short experience, I’ve found R isn’t particularly snappy–even when the data can fit comfortably in memory. I was pretty sure I could beat R’s record count performance handily with C#. And I did. I found some related questions on StackOverflow. A small handful of answers discussed the efficiency of various approaches. I only tried two C# variations: my original attempt, and a second version that was supposed to be faster (the improvement was nominal).

To fact-check Dave (because this blog is about nothing other than making sure Dave is right), I checked the source code to the wc command. That command also streams through the entire file, so Dave’s premise looks good.

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