## Linear Algebra with R – Part II – Vector and Matrix Operations

Transpose The transpose of a matrix means turning rows (columns) into columns (rows). For instance, if the matrix is a vector, Generalizing, if A is of order m x n its transpose, A’ (or A⊤ ) is a matrix of order n x m. To obtain the transpose of a […]

## Linear Algebra with R – Part I – Introduction

Linear algebra is the math of vectors and matrices. Thus, this article has two aims: 1) Introducing linear algebra (vectors and matrices) and 2) showing how to work with these concepts in R Concepts Scalar A scalar is just a single value, an integer or a real number. E.g. 5 […]

## SQL: Joins

Simple queries are useful when we want to explore data or just to have a look at the database structure. But the power of SQL starts when we create complex queries by mixing records from several tables. For instance: List each order placed last year, showing the order amount, the […]

## SQL: Summary Queries

SQL supports data summarization through column functions and the GROUP BY and HAVING clauses. Column Functions A SQL column function takes an entire column of data and produces a single data item that summarizes the column. The most important column functions are: SUM() computes the total of a column. AVG() […]

## SQL: SELECT

Note: All the examples in this article use the Classic Models sample database. SELECT, retrieves data from a database. Probably, the simplest example is:

This statement retrieves the Customer’s name of all distributors in Customer Table. Syntax:

Each select_expr indicates a column that you want to retrieve. […]

## Working with MySQL Workbench

I don’t want to repeat what has already been said by experts DBAs.  If you want to see a lot of “good” information about WorkBench, please visit: http://www.mysql.com/products/workbench/ What I could say is: “we need tools to improve our performance, and MySQL Workbench is one of them”. So, I am going to describe […]

## How to install Classic Models sample database

Sometimes we need to setup a database only to test our implementations. In those cases, it’s useful to have a sample database installed in our MySQL Server (In my case: SuSE Linux Enterprise 11). Classic Models is open source sample database. It means we are free to use it to experiment with other […]

## Being a data scientist

I decided to write a series of articles that could be useful for those who are taking their first steps in data science. Also I use these articles as a summary or a quick reminder about how I did something in the past (we can not remember everything). So, here […]

## Reporting with BIRT

In a project I am working on, we need to visualise some information as Reports. I am going to test the main popular tools, so I wanted to share my little “research”. First tool: BIRT The Business Intelligence and Reporting Tool (BIRT) project provides the BIRT technology platform to create […]

## How to install MySQL on SUSE Linux Enterprise 111

There are several ways to install MySQL on a SUSE Server. For instance, it’s possible to use YaST 2 -both the visual interface and the text mode. Or we can download a rpm file in order to install the exact version we want (http://dev.mysql.com/downloads/repo/suse/). But in this case, we are going […]