Handling plots with rcaller

Using RCaller is a simple way of calling R scripts from Java. Unfortunately image handling routines was not implemented so user must handle this stuff himself. In R the result of a plot object can be saved in a simple way like this:

#Data generating process

x<-rnorm(100, 0, 2)

#we generated a normal sample with mean 0 and standard deviation 2

png("path/to/file.png")

plot.ts(x)

dev.off()

After running this short script, no screen output is produced but path/to/file.png is created as a png image. After calling this script from Java, produced image can be loaded like this:

ImageIcon myIcon = new ImageIcon("/path/to/file.png");

This image can be easly drawn on a swing container using

public void paintComponent(Graphics g) {
    super.paintComponent(g);
    myIcon.paintIcon(this, g, 0, 0);
}

TCP sockets in C Language

A good description for Tcp sockets in C language:

http://www.csc.villanova.edu/~mdamian/Sockets/TcpSockets.htm UPDATE at 2012/31/01 Since, this entry is quite old, but a new entry in our blog would be helpful for those are playing with linux sockets using C. Try this link.

Convert OGV to AVI for youtube

Type this command in linux shell for converting OGV video files to AVI:

mencoder foo.ogv -o foo.avi -oac mp3lame -lameopts fast:preset=standard -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=4000

Converted video is directly uploadable for youtube.

CGI programming with R

Simple Matrix Operations for the C Language

matrix is a simple C library for basic matrix operations. Supported operations are:

• Creating matrices
• Summation
• Subtraction
• Multiplication
• Multiplication with a scaler
• Inverse
• Determinant
• Echelon Form
• Submatrix extraction
• Saving and loading matrices

This is an open source project under the GPL. That means you can use and change it for any purpose but you have to make the source codes public.
The header file and an example are given below. Also you can download the source code by clicking here.

An example is given below:

/*================================================================
  matrix, a simple library for matrix operations.
  Copyright (C) 2010-2011 by Mehmet Hakan Satman.

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License version 2
  as published by the Free Software Foundation.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 

 USA

  The author may be reached at mhsatman@yahoo.com.
 *============================================================*/

#include <stdio.h>
#include <stdlib.h>
#include "matrix.h"

int main()
{
    int n=10;
    int m=10;
    /*
    Creating a matrix with rows n, columns m
    */
    Matrix *m1=Matrix_create(n,m);
    Matrix *m2;
    /*
    Randomizing the matrix.
    */
    int i,j;
    double val=1;
    for (i=0;i<n;i++){
        for(j=0;j<m;j++){
            val=((double)random()/RAND_MAX)*1;
            if(((double)random()/RAND_MAX)<0.5) val*=-1;
            Matrix_set(m1,i,j,val);
        }
    }

    /*
    Dumping the content of the matrix
    */
    Matrix_dump(m1);

    /*
    Getting inverse of the matrix.
    */
    m1=Matrix_inverse(m1);

    /*
    Getting the second column of the matrix
    */
    m2=Matrix_getcol(m1,1);

    /*
    Saving matrices
    */
    Matrix_save(m1,"matrix1.dat");
    Matrix_save(m2,"matrix2.dat");

    /*
    Reloading matrices
    */
    m1=Matrix_load("matrix1.dat");
    m2=Matrix_load("matrix2.dat");

    /*
    Calculating determinant
    */
    printf("Determinant of m1 is %f\n", Matrix_determinant(m1));

    //this will return nan, becase m2 is not a square matrix
    printf("Determinant of m2 is %f\n", Matrix_determinant(m2));

    /*
    Free the memory
    */
    Matrix_delete(m1);
    Matrix_delete(m2);

    printf("OK\n");

    return(0);
}

The main page of this library is http://www.mhsatman.com/