R : Webcrawler Parser with Try-Catch

Well, I felt the need to do some analysis over content hosted on some initial set of web-sites and then aggregate it, plot. I created a very simple and easy parser which would crawl and parse the data read from these websites. I used the try-catch block for fault tolerance and resilience from error (website down, unavailable or trust error, etc). Here is a sample code, where I have used tryCatch and readLines methods :

  
>myUrlStats <- function(urlToCrawl) {
    statData <- tryCatch(
               {
   dataReadFromUrls <- readLines(con=urlToCrawl)
   myWebCrawlParser(dataReadFromUrls)
  },
        error=function(errorMessageStr) {
            message(paste("URL does not seem to exist:", urlToCrawl))
            message("Error message:")
            message(errorMessageStr)
            return(-1)
        },
        warning=function(warningMessageStr) {
            message(paste("URL caused a warning:", urlToCrawl))
            message("Warning message:")
            message(warningMessageStr)
            # Choose a return value in case of warning
            return(NULL)
        },
        finally={
   ##Clean up code
  }
 )
    return(statData)
}


> myWebCrawlParser <- function(dataReadFromURL){
# Do your analysis parsing here
# also like you can mine other outlinks from this data read for further traversing the web-links
return(1)
}


> urlToCrawl <- c(
  "http://superdevresources.com",
     "http://superbloggingresources.com"
     )
> finalReslt<- mapply(myUrlStats, urlToCrawl)

Happy programming!

R: Alternative and easy approach to Data concatenation

Sometimes in R you have the requirement of concatenating/appending data from two sources to create one Super Set, for eg. You may have a list of countries and economic growth indicators, and you want to create a data set which is a super set of this data (AxB), here is how you can do it via simple apply operation:

> myCustColNames
  MyColNames
1          A
2          B
3          C
4          D
5          E
> growthIndicator
[1] "GDP"        "Inflation"  "Population"
> apply(myCustColNames,1, paste, growthIndicator, sep="_")
     [,1]           [,2]           [,3]           [,4]           [,5]          
[1,] "A_GDP"        "B_GDP"        "C_GDP"        "D_GDP"        "E_GDP"       
[2,] "A_Inflation"  "B_Inflation"  "C_Inflation"  "D_Inflation"  "E_Inflation" 
[3,] "A_Population" "B_Population" "C_Population" "D_Population" "E_Population"
> 

Another example can be:

> myCustColNames<-data.frame(MyColNames=LETTERS[1:5])
> myCustColNames
  MyColNames
1          A
2          B
3          C
4          D
5          E
 > apply(myCustColNames,1, paste,seq(1:6), sep="")
     [,1] [,2] [,3] [,4] [,5]
[1,] "A1" "B1" "C1" "D1" "E1"
[2,] "A2" "B2" "C2" "D2" "E2"
[3,] "A3" "B3" "C3" "D3" "E3"
[4,] "A4" "B4" "C4" "D4" "E4"
[5,] "A5" "B5" "C5" "D5" "E5"
[6,] "A6" "B6" "C6" "D6" "E6"
> 

R: Converting a list to a dataframe

Sometimes a function returns a list data type, which you often need to convert to a data.frame data type. To convert the list to data.frame ran the following statement:

 compositeRowOfDataFrame<-do.call(rbind.data.frame, listData)

R deleting rows in a dataframe

To remove all rows from a data frame in R, you can use any of the following ways:

> b
   x  y   Result
1  1  1   B
2  1  2   B
3  1  3   C
4  1  4   A
5  1  5   B
6  1  6   A
7  1  7   C
8  1  8   C
9  1  9   B
10 1 10   C
> deleteRowsVec=c(FALSE)
> b[deleteRowsVec,]
[1] x   y   Result
<0 rows> (or 0-length row.names)

R: How to get current working directory and change it

If you are working on a R project, and you wish to load/save your data in some file, it is important to know which directory you are currently working in, so that you can easily browse or save your data to that directory or may be change it to a specific location. Here are the list of commands to get you going :

> getwd()
[1] "C:/Users/parag/Documents"
> ?setwd
> setwd("X:/Share")
> getwd()
[1] "X:/Share"
> 

WhatsApp call feature is out

The much awaited call feature of WhatsApp is out now and available to all Android users.  After installing the update and opening WhatsApp, you see a new tab for Calls next to the Chats and Contacts tab. Tap on the Calls tab and select the name of the person that you want to call. 
I made some quick phone call in successions to some of my friends and family and found the voice quality at par with similar services like Skype. Currently its available only to Android users. IPhone and Windows phone users would need to wait for some time. 

Windows Server 2003 End of Support

Starting July 14, 2015, Microsoft will end all support and updates for Windows Server 2003. Microsoft hosting an exclusive series of webinars to help you with a smooth transition from Windows Server 2003.

Presenter(s):	Manpreet Madaan and Vishal Mitbawkar.
Language(s):	English.
Product(s):	Microsoft server product portfolio.
Audience(s):	IT Decision Maker, IT Manager, Tech Influencing BDM and Tech Support - Partners.

Webinar Details:

Date: April 02, 2015   Time: 3:00 pm to 4:00 pm

Register here.