Category Archives: CS Courses

SOLID Concepts

Object Oriented Programming Concepts

OOP Clear

Training Set, Validation Set, Test Set

Training Set is a subset of the dataset used to build predictive models.
Validation Set is a subset of the dataset used to assess the performance of model built in the training phase
– It provides a test platform for fine-tuning model’s parameters and selecting the best performing model
– Not all modeling algorithms need a validation set
Test set or unseen examples is a subset of the dataset to assess the likely future performance of a model.
– If a model fits the training set much better than it fits the test set. Overfitting is probably the cause


Binary Classification(two class classification)

true|false, 1|0, -1|+1, male|female

Multi-class classification problems can be seen as binary classification problems.

Model Evaluation:

PHP OOP Project

Basic Simple Project By Me:

By Others:
From OOP Fundamentals udemy Video project:


PHP OOP: Class, Method, Object, Instance, Declare, Echo, Inheritance,Constructor,Access Control,Static!

PHP OOP example described here from edwin’s video:

Inheritance example:


Access control: Public, Private, Protected

Static Data in Class:


Database Interview Questions

Theory site:
Another Resource:

SQL Join – Interview Clear

In below:  The relationship between the two tables is specified by the customer_id key, which is the “primary key” in customers table and a “foreign key” in the orders table:

customer_id first_name last_name email address city state zipcode
1 George Washington 3200 Mt Vernon Hwy Mount Vernon VA 22121
2 John Adams 1250 Hancock St Quincy MA 02169
3 Thomas Jefferson 931 Thomas Jefferson Pkwy Charlottesville VA 22902
4 James Madison 11350 Constitution Hwy Orange VA 22960
5 James Monroe 2050 James Monroe Parkway Charlottesville VA 22902
order_id order_date amount customer_id
1 07/04/1776 $234.56 1
2 03/14/1760 $78.50 3
3 05/23/1784 $124.00 2
4 09/03/1790 $65.50 3

Note that (1) not every customer in our customers table has placed an order and (2) there are a few orders for which no customer record exists in our customers table.

Inner Join Query:


first_name last_name order_date amount
george washington 07/04/1776 $234.56
john adams 05/23/1784 $124.00
Thomas Jefferson 03/14/1760 $78.50
Thomas Jefferson 09/03/1790 $65.50






Good Learning Site for beginners:


Less Important But Okay:

Data Science MOOC (Will do someday)

Data Science: Discrete vs Continuous

Making Predictions with WEKA

How to Save Your Machine Learning Model and Make Predictions in Weka

Decision Tree

Data Mining Deep Study – Confusion Matrix

A confusion matrix shows the number of correct and incorrect predictions made by the classification models compared by actual outcomes (target value) in the data.


Found a good lecture regarding confusion matrix with easy explanation for HIV AIDS. Video is found below and my own drawing regarding this is also given below:


My parents don’t know I was a mad lover of GTA series since my school life(class 4)…When GTA V trailer was released in 2009 after my SSC, I upgraded my pc and waited a lot for releasing of this game but time passed and they delayed to release it. In my university life I was busy with academic stuffs so I barely get chances to play this game and my graphics card got jammed for not using too much. Recently Rockstar Games released Artificial Intelligence and other engineering behind this game. It is a pleasure for me now as I am understanding little bit of the engineering behind this game as a CS graduate. I was their die hard fan once upon a time and still I am. If I get some space in my life to play this game I am sure I can find the peace