Where has the MTP option vanished ?

Recently I ran into a problem, the notification (see the image below)

that usually appears after connecting any android smart phone to laptop using USB for transferring media files, suddenly stopped appearing.
I tried to locate the option and finally got it in a very unusual place. This option is now available under Settings -> Storage ->
and tap the dotted menu on the right 

On some smart phones USB fork symbol appears instead of the dotted menu.

Example .arff files for Weka on Ubunut 14.04

Where are the example ".arff" files for Weka on Ubuntu 14.04?

I recently installed Weka on my laptop having Ubuntu 14.04. For getting familiar with Weka I started locating the example files that come with the Weka package. After several Google queries I found that the example files are located in

/usr/share/doc/weka/examples/

A comprehensive list of files for the Weka package can be found here

How I installed arabtex latex package on ubuntu 13.10

While compiling a latex project, the compiler complained it could not locate the package arabtex. This latex package is used to render Arabic script in pdf. A useful post "Easy installation/removal of a LaTeX package" suggested searching for the package using the command

apt-file -x search '/arabtex.sty$'

The command line prompted "The program 'apt-file' is currently not installed. You can install it by typing: sudo apt-get install apt-file"
Thus I installed apt-file first by

sudo apt-get install apt-file 

after installing the apt-file I again issued the command

 apt-file -x search '/arabtex.sty$' 

This time the terminal responded by

 texlive-lang-arabic: /usr/share/texlive/texmf-dist/tex/latex/arabtex/arabtex.sty

where the part before : i.e. texlive-lang-arabic indicates the name of the package required. Finally I issued the command

 sudo apt-get install texlive-lang-arabic 

to successfully install the package.

Generating a Random m x n sparse matrix in python with given number of ones

A friend of mine Sheraz needed a small code chunk in python that could generate a random sparse matrix. The requirement was to be able to generate a m by n matrix where most of the entries are 0's and the user mentions the number of 1's required. I am listing down the code that was written by me and later improved by Sheraz for the purpose of preserving it by making it accessible online. The function genmatrix takes 3 arguments en is required number of 1's, s and n correspond to the number of rows and columns of matrix a

from numpy import *
from random import *
from math import *

def genmatrix(en,s, n):
    count=0
    S=range(s)
    N=range(n)   
    a = zeros(shape=(s,n))
    while (count < en):
        i= randint(0,s-1)
        j= randint(0,n-1)
        print i, j
        if (i in S) and (j in N):
            a[(i,j)]=1
            S.remove(i)
            N.remove(j)
            count +=1
    #print a
    #print [sum(a[i]) for i in range(s)]
    #print [sum(a[:,i]) for i in range(n)]
    return a 

Ubuntu Terminal Commands

Just wanted to keep track of commands and configurations I frequently forget and google.


For unzipping a .zip file via terminal

unzip file.zip -d destination_folder

For copying files using ssh

scp [[user@]from-host:]source-file [[user@]to-host:][destination-file]

from-host: Is the name or IP of the host where the source file is, this can be omitted if the from-host is the host where you are actually issuing the command

user: Is the user who has the right to access the files and directories to be copied in case of from-host, and the user who has the rights to write in case of to-host

source-file: Is the file or files that are going to be copied to the destination host, it can be a directory but in that case you need to specify the -r option to copy the contents of the directory

destination-file: Is the name that the copied file is going to take in the to-host, if none is given all copied files are going to keep its names