R Notes

Matrices
Tip #1 
Declaration - matrix (0,3,4)
3 rows, 4 columns and values 0
print[1,1]

Tip #2
Vector a <- 1:12 (To fill Matrix)
matrix(a, 3, 4)

Tip #3

Assigning, Fetching & Printing values
plank <- 1:8 - Create Vector
dim(plank) <- c(2,4) - Assign Dimension
print(plank) - Print values
plank[1,4] <- 0 - Assign value
plank[2,] - Fetch all 2nd row values

Tip #4 - Plotting Matrix

elevation <- matrix(2,5,10)
contour(elevation) - 2D representation
persp(elevation) - 3D representation
persp(elevation, expand = 0.2)

Statistics
Tip #1 - Mean computation
a <- c(1,2,3,4,5)
mean(a)
barplot(a)
median(a)

Tip #2
Horizontal line across plots
abline(h=mean(a))
abline(h=median(a))

Tip #3 
Standard Deviation
deviation <- sd(a)

Factors
Tip #1 
R has special collection called factors
chests <- c('gold', 'silver', 'gems', 'gold', 'gems')
types <- factor(chests)
print(types)

Data Frame
Similar to Database
Tip #1 - Loading data from files
read.csv("data.csv")
read.table("a.txt",sep="\t")

Tip #2 - Merge Data Frames
data1 <- read.csv("data.csv")
data2 <- read.table("a.txt",sep="\t")
merge(x = data1, y = data2)

Real World Examples
Data1 <- read.csv("a.csv")
Data2 <- read.table("b.txt", sep="  ", header=TRUE)
TargetData <- merge(x = Data1, y = Data2)
plot(TargetData$Data1, TargetData$Data2)

More Reads
R Programming Examples
R Time Series

R Programming Examples
R Time Series

Happy Learning!!!

R Online Learning

I prefer to switch topics when I find it tricky to focus on one topic. I found R language easy, simple and great to get started. Codeschool has a beautiful self learning portal. This lists cheat sheet and fundamentals working with R. Capturing some of notes for my future reference.

Using R

Tip #1 - Assignment
x <- 42
y <- "Hello"

Tip #2 - Expression
5==10
5>10

Tip #3 - Arithmetic operations
2+2
3*3

Tip #4 - Functions
sum(1,2)
sum(1,2,3,4)

Help

Tip #5 - File I/O
list.files()
source(filename)

Vectors

Tip #1 - Vector
List of Values - vector represented by c(2,3,4)
List of Strings - vector represented by c('a','b','c')
List with multiple data types - vector represented by c(1,'a', TRUE)

Tip #2 - Sequence Vectors
Representing sequence of numbers m to b by m:n
 - seq(10,50)
 - seq(10,50,5) - With increment step 5
 - seq(50,10) - Reverse sequence representation

Tip #3 - Assigning Vectors (Single Quotes)
sentence <- c('walk', 'the', 'plank')
sentence[3]
a <- c (1,2,3)
b <- c (1,2,3)

Sample Vector Operations
a+1
a*2
a+b

x <- seq(1, 20, 0.1)
y <- sin(x)

Tip #4
c for combine vectors
c(1,2,3)

Tip #5
Plotting Vectors
vectorCoordinates <- c(4, 5, 1)
barplot(vectorCoordinates)
barplot(1:100)

x <- seq(1, 20, 0.1)
y <- sin(x)
plot(x,y)

Great Learning Sites
Statsmethod
Code School

Happy Learning!!!

Recommendation Algorithm Analysis

Item to Item Rating based on customer’s purchase of products

The formula for comparison is dot product divided by product of vector lengths
In the example for two sets Book and DVD

• Book – (1,1,1) – Set A consider it as (A1, A2, A3)
• DVD – (1,0,0) – Set B consider it as (B1, B2, B3)

Formula works as

• (A1.B1 + A2.B2 + A3.B3) /sqrt((A1 square + A2 Square + A3 Square)( B1 square + B2 Square + B3 Square))
• (1)/sqrt((3).sqrt(1)
• 1 / 1.732
• 0.577

     Item to Item Comparison based on customer ratings

The formula for comparison is dot product divided by product of vector lengths

In the example for two sets Book and DVD

• Book – (4,3,5) – Set A consider it as (A1, A2, A3)
• DVD – (1,0,0) – Set B consider it as (B1, B2, B3)

Formula works as 

• (A1.B1 + A2.B2 + A3.B3) /sqrt((A1 square + A2 Square + A3 Square)( B1 square + B2 Square + B3 Square))
• (4)/sqrt((16+9+25).sqrt(1)
• 4/7.07
• 0.565

Analysis - By comparing multiple items the items that yield the maximum value would be recommended to the customer

Happy Learning!!!

Good Courses

Bookmarking two useful courses on Statistics and Machine Learning

Machine Learning Coursera

Statistics 110

Statistics and Data

Statistics One

Descriptive Statistics

Good One - How to Become a Data Scientist for Free

Happy Learning!!!

Inverse Matrix Computation

Matrix A Represented by

Reference - Link

Happy Learning!!!

Matrix and Determinants (Basics)

Back to School and basics. These posts are for my on-line references.

Matrix

• Rectangular Array of Numbers in rows and columns
• Example - [5,2,-3]
• Order of Matrix is represented as Rows X Columns

Types of Matrices

• Row matrix (1 Row, any number of columns)
• Column matrix (1 Column, Multiple Rows)
• Diagonal matrix (Square matrix, Except diagonal elements every other elements are 0)
• Scalar matrix (Square matrix & Diagonal matrix in which all diagonal elements are same)
• Identity matrix - Denoted by I - Diagonal Elements are 1 (Square & Diagonal Matrix)
• Transpose of matrix - Matrix where rows and columns are interchanged

        [ 1, 1, 1 ]

A  = [ 2, 2, 2 ]

        [ 3, 3, 3 ]

Transpose is

A' =   [ 1, 2, 3 ]

          [ 1, 2, 3 ]

         [ 1, 2, 3 ]

Addition of Matrices

• They should be of same order
• Add Corresponding elements

A =   [2,3,5]

         [5,7,-2]

        [5,3,0]

B =    [7,-1,5]

          [0,2,3]

         [7,5,2]

Result ( Add Corresponding elements in same positions)

A + B =     [9,2,10]

         [5,9,1]

               [12,8,2]

Subtraction (similar to addition)

• Order needs to match

A = [7,-2]

       [0,3]

B = [0,2]

[3,5]

A - B = [7,-4]

          [-3,-2]

Scalar Multiplication

• Multiplying constant with a Matrix
• Every Element of Matrix Multipled

c = [3,5]

[-2,-10]

-2c =  [-6,-10]

  [4,20]

Matrix Multiplication

• A (m x n)
• B (n x p)
• Columns in a (n) = Number of Rows in B (n)

A = [3,5]

[7,2]

[2,3]

B = [-2,5]

[3,7]

AB = Operate First Row (Operate) Multiple with First Coulmn

A = [3,5] --->

[7,2]

[2,3]

Select Column 

B = [-2,5] 

[3,7]  

  = [ 3 X -2 + 5 X 3,  3 X 5 + 5 X 7 ]

[ 7 X -2 + 2 X 3,  7 X 5 + 2 X 7 ]

[ 2 X -2 + 3 X 3,  2 X 5 + 3 X 7 ]

 = [9,50]

[-8,49]

[5,31]

Matrix Multiplication is not commutative

Determinant of Square Matrix

+  -

A = [5,6]

[3,-4]

|A| = [Multiply Principal Diagonal Elements ] - [Subtract the Next Diagonal Elements]

= (5 X -4) - (3 X 6)

      = -20 - 18

      = -38

Determinant of 3 X 3 Matrix

        +,-,+

A =  [3,-2,1]

       [2,3,4]

       [2,5,4]

= +3 X [3,4] - (-2) X [2,4] + 1 X [2,3]

                  [5,4]               [2,4]           [2,5]

= 3(12-20) + 2 (8-8) + 1(10-6)

       = -24 + 0 + 4

       = -20

References - Link

Happy Learning!!!

Mobile Test Automation Startups

Interesting start-ups coming up in this space

• AppThwack
• AppliTools
• Testim

Other high visible companies include saucelabs, browserstack, perfecto mobile etc..

Happy Learning!!

Weekend Tech Talks

Excellent Talk on Android Testing and Automation Fundamentals

 

Good Notes / Screenshots from Session

Why Automated Testing, What does it Solve ?

What are pros / cons of Automation vs Manual Test Efforts ?

How to use Record / Play back tools ?

Mobile testing options Emulators / Devices ?

Evaluating a Commercial Tool ?

Happy Learning!!!

Setting up Jmeter Code base on Windows

Today Dinesh & myself had a good learning time in setting up Jmeter code base. There are not too many blogs / notes. This is a basic draft capturing the steps at high level. Good one for Windows background developers :).

1. Download Jmeter Zip code from Github
2. Create Project with same name. Eclipse - eclipse-jee-kepler-R-win32-x86_64
3. Setup Java Project

4. Set Ant Perspective

5. Execute Download Jars option as Ant Build (Run as Ant Build)

6. Download all the JAR files from link https://www.bouncycastle.org/latest_releases.html (Below mentioned versions)

Output path specified as below

7. Java Compiler Settings

8. Following code changes done for non matching jars

9. Below value set at Code Level

Happy Learning!!!

Interesting Sites

Two new interesting sites

Security Tools and Market Share of them - @ sectoolmarket 

Collection of useful tech talks available @ techtalkshub 

Happy Learning!!!