Hi Guys,
Welcome Back!
Today another little step towards the machine learning with a first lesseon about the R language.
Introduction
Yes, you remember very well!We already talked about SQL Server and the R language some posts ago.
In a first post we talked about how to install the machine learning services in SQL Server
While in a second post we talked briefly about using R language to read data from SQL Server
Now if you want to do another step towards the machine learning you really need to learn a bit of R language.
So today I will show some very basic concepts about this really powerful and widely used in data science, the R language.
We will se how to do and assignment, how to use array, vector and matrix.
Are you Ready?
Let's go!
A Basic lesson about R!
R is a very powerful language and it is also free and expandible through varius library.
I suppose you have already installed R and so you a ready to execute the R Console.
You can start typing some after the ">" prompt
You can, for example, type the text below and then press enter:> 8+2
You will obtain:
[1] 4
Type now:
> log(2)
and you will receive:
[1] 0.6931472
Ok R is a fantastic calculator!!! But let’s continue...
Variables
Some note:
- R declare automatically variables
- The assignment is done with the <- command
- R is case sensitive
You can declare a variable a and assign the value 4 typing:
> a <- 4
Now if you type:
> a
You will obtain the result of the variable "a"
[1] 4
Now if you type:
> a
You will obtain the result of the variable "a"
[1] 4
Vectors (Arrays)
R can manage vectors (array) in an easy way
Type for example the command below:
List <- c(1, 2, 2.5, 9, 9, 9, 5, 2)
Through the “c” concatenate command you declare a Vector
In order to show the content og the vector just type:
> List
[1] 1.0 2.0 2.5 9.0 9.0 9.0 5.0 2.0
Nice!
You can also get a subset of your vector with this syntax:
> List [1:3]
[1] 1.0 2.0 2.5
Or you can easily sum the values of all the elements of your vector:
sum(List) [1] 440.5
Another way to declare a vector is this:
> W <- vector(length = 2)
> W[1] <- 10
> W[2] <- 12
[1] 1.0 2.0 2.5 9.0 9.0 9.0 5.0 2.0
Nice!
You can also get a subset of your vector with this syntax:
> List [1:3]
[1] 1.0 2.0 2.5
Or you can easily sum the values of all the elements of your vector:
sum(List) [1] 440.5
Another way to declare a vector is this:
> W <- vector(length = 2)
> W[1] <- 10
> W[2] <- 12
And now i will show you how to manage Matrix!
Matrix
You can declare a matrix through this Syntax:
> Mat <- matrix(nrow = 8, ncol = 4)
To display the Matrix content:
> Mat
[,1][ ,2][ ,3][ ,4]
[1,] NA NA NA NA
[2,] NA NA NA NA
[3,] NA NA NA NA
[4,] NA NA NA NA
[5,] NA NA NA NA
[6,] NA NA NA NA
[7,] NA NA NA NA
[8,] NA NA NA NA
Matrix
You can declare a matrix through this Syntax:
> Mat <- matrix(nrow = 8, ncol = 4)
To display the Matrix content:
> Mat
[,1][ ,2][ ,3][ ,4]
[1,] NA NA NA NA
[2,] NA NA NA NA
[3,] NA NA NA NA
[4,] NA NA NA NA
[5,] NA NA NA NA
[6,] NA NA NA NA
[7,] NA NA NA NA
[8,] NA NA NA NA
And set a value with:
Mat [1, 1] <- 2.0
Mat [1, 1] <- 2.0
That’s all for today!
I hope you liked this post and found it useful.
Luca
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