Learn R : Statistical Programming Language Part 1

    SQL Server 2016 supports running R code in SQL Server using stored procedures. This feature created a new way to query the data in SQL Server. Microsoft introduced this feature under R Services. With Python support in SQL Server 2017, Microsoft changed the package name from R Services to Machine Learning package. To be able use or explore this functionality, you need to know R.
    I am going show you the basics of R language in this post. Please check my older blog about how to setup R Services/Machine Learning in SQL Server side and client side to learn about the setup process. You don't need to install anything today to learn the basics of R. We will worry about querying SQL data later. I am going to use R-Fiddle for demos, It's free and you don't need to install anything.

R Expressions

Let's start with variables, to store data in a variable you need to use  <-

R Fiddle

       As you can see, you don't need to specify a type for a variable, I just give a name without type  to call it later. Also just like JavaScript you can re-assign any value to any variable at any time. You can use T as a shorthand for TRUE and F as a shorthand for FALSE.

R Functions

     Nothing is new here, To call a function, you need to type its name, followed by one or more arguments to that function in parenthesis. Here is some basic functions.

R Fiddle

     rep() function a value multiple times.To get help about any function you can call help(function_name), To get an example of a usage a function you can call example(function_name).

To repeat a value, you can use rep function.

R Vectors

     Vectors are list of values. R uses vectors for many of its operations and graphs. Vector's values can be any type as long as they are all the same type! Here are some samples for creating array of values by using c function. c is short for Combine.

R Fiddle

     As you can see, when you mix the types in the list, R converts all of the values into string type.
If you need a sequence of numbers, you can create it with start:end notation. Here is an example using : notation to create a vector.

R Fiddle

You can do the same thing with seq() function. Seq() function allows you to change increments.

Click here to try it yourself in R Fiddler

    We can use the index number of a vector to access an individual value in a vector. Unlike many languages R's vector indices start with 1. To get the first value of a vector, you need to pass 1 rather than 0. You can insert/edit vector values by using start:end notation too.

R Fiddle

      If you like to give names to the vectors items, we need to create another vector and attach it to our current vector.

R Fiddle

     We can do all kind of calculations with vectors, Here is some examples. Since R is an analytic language, It doesn't surprise me to have this kind of functionality.

R Fiddle

      R Fiddle is a great tool and location to practice R, Visual R Tools is a great Visual Studio addition if you like to use Visual Studio. Extension is available in Community version, so you don't need to have full paid version to practice and learn R. I will continue to write about R in my next posts.