A Fine Slice Of SQL Server
Tomaz Kastrun shows how to use rvest to read the SQL Saturday website and parse schedule details:
I wanted to check a simple query: How many times has a particular topic been presented and from how many different presenters.
Sounds interesting, tackling the problem should not be a problem, just that the end numbers may vary, since there will be some text analysis included.
Read on for the code and some analysis.
Comments closedThat’s when you remember it… Your server isn’t connected to the internet!
Pretty normal, but in your enthusiasm you completely forgot that SQL Server needs to download some binaries for the R and Python components you so desperately want on your precious machine!Luckily, the installer comes to your rescue and shows you where to download those binaries it needs.
Turns out however… This link only is for one R component and the installer won’t let you pass to the next screen!
Read on for the answer.
Comments closedAntonio Sánchez Chinchón shows how to draw Clifford attractors in R:
From a technical point of view, the challenge is creating a data frame with all locations, since it must have 10 milion rows and must be populated sequentially. A very fast way to do it is using
Rcpppackage. To render the plot I use ggplot, which works quite well. Here you have the code to play with Clifford Attractors if you want:
Click through for the code, as well as sample output images.
Comments closedDave Mason figures out how to create multiple result sets with SQL Server ML Services:
Of course for this strategy to work, I’d have to know ahead of time how many data frames/HTML tables there are. Hmmm. Can dynamic T-SQL help me here? If I could find out at run time how many data frames there are, and which ones I may or may not want, then why not? Here’s some R code that reads HTML tables into a variable as a list of data frames(line 8), iterates through the list (starting at line 18), decides if the HTML table has any data in it (lines 21, 24), and adds the HTML table number (the element number in the list) to a different data frame (line 27). The output shows us we would want HTML tables 1, 2, and 4. (Yeah, I really didn’t want #4. But that can be fixed by enhancing the R code to be more selective. Let’s just go with it for now.)
The method is a bit disappointing (and it’s arguably worse for inputs); I do hope the ML Services team can improve upon this experience.
Comments closedDavid Smith points out a cheat sheet for dealing with strings in R:
The RStudio team has created another very useful cheat sheet for R: Working with Strings. This cheat sheet provides an example-laden menu of operations you can perform on strings (character verctors) in R using the stringr package. While base R provides a solid set of string manipulation functions, the stringr package functions are simpler, more consistent (making them easy to use with the pipe operator), and more like the Ruby or Python way of handling string operations.
Click through for a link to the PDF.
Comments closedRobert Sheldon has a workaround for SQL Server R Services’s limitation of a single input data set:
Despite the ease with which you can run an R script, the sp_execute_external_script stored procedure has an important limitation. You can specify only one T-SQL query when calling the procedure. Of course, you can create a query that joins multiple tables, but this approach might not always work in your circumstances or might not be appropriate for the analytics you’re trying to perform. Fortunately, you can retrieve additional data directly within the R script.
In this article, we look at how to import data from a SQL Server table and from a .csv file. We also cover how to save data to a .csv file as well as insert that data into a SQL Server table. Being able to incorporate additional data sets or save data in different formats provides us with a great deal of flexibility when working with R Services and allows us to take even greater advantage of the many elements available to the R language for data analytics.
Another option is using the rodbc package to connect back to SQL Server to retrieve more data.
Comments closedDamian Rodziewicz looks at the new promises package in R:
Citing Joe Cheng, our aim is to:
- Execute long-running code asynchronously on separate thread.
- Be able to do something with the result (if success) or error (if failure), when the task completes, back on the main R thread.
A promise object represents the eventual result of an async task. A promise is an R6 object that knows:
Whether the task is running, succeeded, or failed
The result (if succeeded) or error (if failed)
This looks pretty exciting. H/T R-Bloggers
Also, Sebastian Warnholz has a post on promises and closures in case you’re not familiar with the concepts:
Every argument you pass to a function is a promise until the moment R evaluates it. Consider a function g with arguments x and y. Let’s leave out one argument in the function call:
g <- function(x, y) x g(1) ## [1] 1
R will be forgiving (lazy) until the argument y is actually needed. Until then y exists in the environment of the function call as a ‘name without a value’. Only when R needs to evaluate y a value is searched for. This means that we can pass some non-existent objects as arguments to the function g and R won’t care until the argument is needed in the functions body.
Read the whole thing. Once again, H/T R-Bloggers
Comments closedSibanjan Das has started a new series on text mining in R:
Next, we need to preprocess the text to convert it into a format that can be processed for extracting information. It is essential to reduce the size of the feature space before analyzing the text. There are various preprocessing methods that we can use here, such as stop word removal, case folding, stemming, lemmatization, and contraction simplification. However, it is not necessary to apply all of the normalization methods to the text. It depends on the data we retrieve and the kind of analysis to be performed.
The series starts off with a quick description of some preprocessing steps and then building an LDA model to extract key terms from articles.
Comments closedI ran into an error after installing SQL Server 2017:
After installation completed, the DBA enabled SQL Server 2017 Machine Learning Services, but as soon as I tried to run a simple R script, it stalled for about 30 seconds and then I got an error:
Msg 39012, Level 16, State 1, Line 0
Unable to communicate with the runtime for ‘R’ script. Please check the requirements of ‘R’ runtime.
STDERR message(s) from external script:
Error: could not find function “rxSqlUpdateLibPaths”
Execution halted
Click through for the solution.
Comments closedAnish Sing Walia walks us through creating a dashboard using Shiny:
Shinyis an amazing R package which lets the R developers and users build amazing web apps using R itself. It lets the R users analyze, visualize and deploy their machine learning models directly in the form of the web app. This package lets you host standalone apps on a webpage or embed them in R markdown documents or build dashboards and various forecasting applications. You can also extend your Shiny apps with CSS themes, htmlwidgets, and JavaScript actions.Shinylets us write client-side front-end code in R itself and also lets users write server-side script in R itself. More details on this package can be found here.I recently learned Shiny and started developing a web application using it.And since then I have been in love with it and have been using it in each and every data science and analytics project. The syntax is super easy to understand and there are lots of amazing articles and documentation available for you to learn it and use it. I personally had a background of developing full-stack web applications using HTML, CSS and javascript and other JS based scripting languages so I found the syntax easy.
I keep meaning to learn Shiny and someday I will, just to prove to my intern that she’s not the only one here who can…
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