Recruiters are spellbound by this incantation – Hadoop. So I took the plunge and started working with it. I haven’t made much progress but now I use this Sandbox VM and follow the tutorial steps.

## Machine learning on Big data

I just viewed the webinar conducted by SkyTree. This particular slide has some information about the evolution of Machine Learning.

Let $J(\theta) = \theta^3$. Furthermore, let $\theta = 1$ and $\epsilon=0.01$. You use the formula

$(J(\theta+\epsilon )- J(\theta-\epsilon))/2\epsilon$

to approximate the derivative. What value do you get using this approximation ?(When $\theta=1$,the true, exact derivative is
$d/d\theta J(\theta) = 3$ ).

The Octave code that I used to solve this is

((1+0.01)^3-(1-0.01)^3)/(2*0.10)


3.0001

## Logistic Regression

I just finished the code for a Logistic Regression classification model. I worked on a Card transaction processing system and there was a requirement for identifying whether a card transaction is fradulent or not. We did not use any classification model but if we had had a training set of historical data we could have used this learning algorithm.
Most of the time it is the lack of skills that affects software projects that I have been involved with.

### Cost function for Logistic Regression

$J(\theta) = 1/m \sum_{i=1}^{m}[-y^{(i)} log( h_\theta(x^{(i)}) - (1-y^{(i)})log( 1 - h_\theta(x^{(i)}))] ;$

$(\partial J(\theta)/\partial \theta_j ) = 1/m \sum_{i=1}^{m} ( h_\theta(x^{(i)}) - y^{(i)}) x^{(i)}_j$

This is the plot generated by the course material based on my code. The line is a decision boundary that shows which exam scores ensure admittance. We can use historical card transaction data in place of this.

This classificatio model can predict which card transactions could be fradulent based on a probability calculated by the algorithm. So here instead of plotting exam scores on the axes we can plot card transaction data.

## Varargs

Is this confusing code ? I was stumped for a few seconds.

public class PassThreeValues {
static void calculateSomeThing(int one, int... values){}

public static void main( String... argv ){
calculateSomeThing(1,2,3);
}