Caching an Inverse of a Matrix Using R

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Caching an Inverse of a Matrix Using R 

Matrix inversion is usually a costly computation and there may be some benefit to caching the inverse of a matrix rather than computing it repeatedly.

This is an example code to cache an inverse of a matrix which then called if:

1. The new matrix computation similar to the previous matrix

2. Matrix is invertible — Read Invertible Matrix

3. The structure and content of the new matrix is equal to previous

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The program consists of two functions

1. A function to cache the matrix and the inverse. It is similar to getter and setter in many programming languages like Java and C.
2. A function which will be call for the computational process of the matrix

Here are parts of the code:

Setting the matrix

Setting the inverse matrix

Verification on the matrix

Setting the new inverse

Complete source code is reachable at https://github.com/masteramuk/ProgrammingAssignment2

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Reading entire URL content is really easy using R

In my good old days, reading the entire content of a website is not easy. The process of web scraping and getting the required data requires lots of programming and a few tools. A friend of mine even developed and sold the tool which he called it (during the development) as myrobot. He developed using PHP.

Now, it is much easier and one of the many ways is using R.

Here are the steps (which requires you to write ONLY two lines of code)

1. Connect to the website using URL command
   con <- url ([the website url], “r”)
2. Then, read the website
   x <- readLines(con)
3. Do whatever you wish with the data. In this example, I print out the head of the website and also copy the whole content to a file.
   head(x)
   dput(x, “readFromUrlExample.html”)

There you go.

The sample source code can be retrieved at 

https://github.com/masteramuk/LearnR-Coursera/blob/master/sample-ReadFromUrl.R

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