sine wave in java2D graphics.

[ozzyman]

Look at these two graphs

y=x2 (quadratic)
http://www.bbc.co.uk/schools/gcsebit...s/graph_24.gif

y=-x3 (cubic)
http://www.bbc.co.uk/schools/gcsebit...s/graph_17.gif

which one looks more like a sine wave?

[JosAH]

would u mind explaining the curves plz.. it is necessary for my project works . im doing my final year project and last date is next monday

Forget about those Bezier curves; define two arrays instead:

double[] x;
double[] y;

... and fill them such that sin(x[ i ]) == y[ i ]; apply the scaling I defined before and you have all your points needed to draw a sine wave.

kind regards,

Jos

[noobplus]

Forget about those Bezier curves; define two arrays instead:

double[] x;
double[] y;

... and fill them such that sin(x[ i ]) == y[ i ]; apply the scaling I defined before and you have all your points needed to draw a sine wave.

kind regards,

Jos

ty boss, but what is the syntax to plot or draw the scaled values

[noobplus]

ty boss, but what is the syntax to plot or draw the scaled values

between, do u know signal processing.. can we apply fast fourier transform in java.. ? this is also a part of my project

[noobplus]

Look at these two graphs

y=x2 (quadratic)
http://www.bbc.co.uk/schools/gcsebit...s/graph_24.gif

y=-x3 (cubic)
http://www.bbc.co.uk/schools/gcsebit...s/graph_17.gif

which one looks more like a sine wave?

ty , and do u know signal processing.. can we apply fast fourier transform in java.. ? this is also a part of my project

[Fubarable]

Yes there are FFT libraries out there that are best found via Google.

[noobplus]

Yes there are FFT libraries out there that are best found via Google.

tyvm.. could u suggest me, what to search on google

[Fubarable]

tyvm.. could u suggest me, what to search on google

No. I'm sure you're as clever as I am and will play with terms til you find one that works well for you.

[noobplus]

No. I'm sure you're as clever as I am and will play with terms til you find one that works well for you.

library, u mean classes or packages ? or something else

[JosAH]

No. I'm sure you're as clever as I am and will play with terms til you find one that works well for you.

Nope, sorry 'squire; nothing relevant showed up; not even for "ole busstop", "dolphin", "mammalian protuberances", "biscuit barrel" or "tomato"; that Google thing is worthless ...

kindest regards,

Jos (<--- slightly silly on the right side (1247 points) ;-)

[Fubarable]

Nope, sorry 'squire; nothing relevant showed up; not even for "ole busstop", "dolphin", "mammalian protuberances", "biscuit barrel" or "tomato"; that Google thing is worthless ...

Of course nothing's showing up you ninny. "busstop" is hyphenated! Gosh don't they teach you nuthin' in the Netherlands??

[Fubarable]

library, u mean classes or packages ? or something else

But seriously, I have not used FFT with Java (just with Turbo Pascal years ago), but I've seen libraries listed by the hundreds. I'm sure if you do a reasonable search on some good terms you'll come up with several promising leads.

[JosAH]

As in "bŭßƨƮǒƤ" 'squire? But then it doesn't even look like "muffin" ...

kindest regards,

Jos

[noobplus]

Nope, sorry 'squire; nothing relevant showed up; not even for "ole busstop", "dolphin", "mammalian protuberances", "biscuit barrel" or "tomato"; that Google thing is worthless ...

kindest regards,

Jos (<--- slightly silly on the right side (1247 points) ;-)

i've done scaling , and dont know ow to plot em next.. heres my coding

import java.io.*;

class fourier extends operations
{
  fourier(String filename, int ntrm)
  {
    boolean debug = true;
    double Pi = 3.1415926535897932384626433832795028841971;
    double x[] = new double[100];
    double y[] = new double[100];
    double a[] = new double[100];
    double b[] = new double[100];
    double xmin, xmax, ymin, ymax, xs, xs1, xs2;
    double err, avgerr=0.0, rmserr=0.0, maxerr=0.0;
    double sum, sumsq=0.0;
    int npts, index, last;
    double tpi = 2.0*Pi;
    double dx, ti;
    FileReader file_in;
    BufferedReader in;
    String input_line, intStr;

    // read data 
    try
    {
      file_in = new FileReader(filename);
      in = new BufferedReader(file_in);
    }
    catch(Exception e)
    {
      System.out.println("read unable to open file "+filename);
      return;
    }
    npts = 0;
    try
    {
      input_line = in.readLine();
      // System.out.println("line="+input_line);
      while(input_line!=null)
      {
	index = 2; // x allow for two blanks
	last = input_line.indexOf(' ',index);
        // System.out.println("xindex="+0+", xlast="+last);
        intStr = input_line.substring(0,last);
        // System.out.println("xstring="+intStr);
	x[npts] = Double.parseDouble(intStr);
	index = last+1; // y
	last = input_line.length();
        // System.out.println("yindex="+index+", ylast="+last);
        intStr = input_line.substring(index,last);
        // System.out.println("ystring="+intStr);
	y[npts] = Double.parseDouble(intStr);
        if(debug)
           System.out.println("npts="+npts+", x="+x[npts]+", y="+y[npts]);
        npts++;
        input_line = in.readLine();
        // System.out.println("line="+input_line);
      }
      file_in.close();
    }
    catch(Exception e)
    {
      System.out.println("read exception"+e);
      return;
    }

    if(ntrm==-1) ntrm = npts;
    ntrm = Math.min(ntrm,(npts-2)/2);
    System.out.println(npts+" points read, using "+ntrm+" terms");

    xmin = x[0];
    xmax = x[0];
    ymin = y[0];
    ymax = y[0];
    for(int j=1; j<npts; j++)
    {
      xmin = Math.min(x[j],xmin);
      xmax = Math.max(x[j],xmax);
      ymin = Math.min(y[j],ymin);
      ymax = Math.max(y[j],ymax);
    }
    System.out.println("xmin="+xmin+", xmax="+xmax+
                       ", ymin="+ymin+", ymax="+ymax);

    // integration, simple trapezoidal rule 
    System.out.println("coefficients");
    for(int i=0; i<ntrm; i++)
    {
      a[i] = 0.0;
      b[i] = 0.0;
      ti = (double)i;
      for(int j=0; j<npts-1; j++)
      {
        xs1 = (x[j]-xmin)/(xmax-xmin);
        xs2 = (x[j+1]-xmin)/(xmax-xmin);
        dx = xs2-xs1;
        a[i] = a[i] + dx*(y[j]*Math.cos(ti*tpi*xs1)+y[j+1]*
                               Math.cos(ti*tpi*xs2));
        b[i] = b[i] + dx*(y[j]*Math.sin(ti*tpi*xs1)+y[j+1]*
                               Math.sin(ti*tpi*xs2));
      }
      System.out.println("a["+i+"]="+a[i]+", b["+i+"]="+b[i]);
    }
    System.out.println(" ");
    // check fit 

    for(int j=0; j<npts; j++)
    {
      sum = 0.0;
      sumsq = 0.0;
      xs = (x[j]-xmin)/(xmax-xmin);
      for(int i=0; i<ntrm; i++)
      {
        ti = (double)i;
        sum = sum + a[i]*Math.cos(ti*tpi*xs) + b[i]*Math.sin(ti*tpi*xs);
      }
      err = y[j]-sum;
      sumsq = sumsq + err*err;
      avgerr = avgerr + Math.abs(err);
      maxerr = Math.max(Math.abs(err),maxerr);
      if(debug) System.out.println("y["+j+"]="+y[j]+", approx="+sum+
                                   ", err"+err);
    }
    rmserr = Math.sqrt(sumsq/(double)npts);
    avgerr = avgerr/(double)npts;
    System.out.println("avgerr="+avgerr+", rmserr="+rmserr+", maxerr="+maxerr);
    System.out.println("fourier.java finished ");
  } // end constructor fourier

  public static void main (String[] args)
  {
    String filename;
    int ntrm = -1;
    int argc = args.length;

    System.out.println("fourier.java running  ");
    if(argc>1) // file and ntrm 
    {
      filename = new String(args[0]);
      ntrm = Integer.parseInt(args[1]);
      System.out.println("fourier series of "+filename+" for "+ntrm+" terms");
      new fourier(filename, ntrm);
    }
    else if(argc>0) // just file, all terms 
    {
      filename = new String(args[0]);
      System.out.println("fourier series of "+filename+" for all terms");
      new fourier(filename, ntrm);
    }
    else
    {
      ntrm = 6;
      filename = new String("curve.dat");
      System.out.println("fourier series of "+filename+" for "+ntrm);
      new fourier(filename, ntrm);
    }
  } // end main  
} // end class fourier


class operations extends fourier
{
public static int a1[i],b1[i],as[i],bs[i];
	void scaling(a[],b[]){
		a1[i]=(a[i]-0)/(2*math.PI-0);//dmax is 2pi dmin is zero
		b1[i]=(b[i]-0)/(1-0);//cmax is 1 cmin is zero
		as[i]=a1[i]*(SXmax-SXmin)+SXmin ;   //sxmin,max not set yet,... will set it based on screen values..
		bs[i]=b1[i]*(SYmax-SYmin)+SYmin; }
}

[JosAH]

i've done scaling , and dont know ow to plot em next..

If you have arrays 'sx' and 'sy' containing the scaled points and if you have a Graphics object 'g' (so you have something to draw on), all you have to do is 'connect the dots':

for (int i= 1; i < sx.length; i++)
   g.drawLine(sx[i-1], sy[i-1], sx[i], sy[i]);

Read the API documentation for the Graphics class for details.

kind regards,

Jos

[noobplus]

If you have arrays 'sx' and 'sy' containing the scaled points and if you have a Graphics object 'g' (so you have something to draw on), all you have to do is 'connect the dots':

for (int i= 1; i < sx.length; i++)
   g.drawLine(sx[i-1], sy[i-1], sx[i], sy[i]);

Read the API documentation for the Graphics class for details.

kind regards,

Jos

"sx" and "sy" do u mean the "a[]" and "b[]" present in my codings? or a new scaling values are required? ..
sorry for this silly doubt, but it explains me more :P
regards

[JosAH]

"sx" and "sy" do u mean the "a[]" and "b[]" present in my codings? or a new scaling values are required? ..
sorry for this silly doubt, but it explains me more :P
regards

Looking at your code I'd say that 'as' and 'bs' contain the scaled points.

kind regards,

Jos

[noobplus]

Looking at your code I'd say that 'as' and 'bs' contain the scaled points.

kind regards,

Jos

oh yeah tyvm boss, and thx again for the "g.drawLine" :]

[noobplus]

Looking at your code I'd say that 'as' and 'bs' contain the scaled points.

kind regards,

Jos

hi again..
i typed "g.drawLine " on eclipse.. it says the command doesn't support double datatypes, and supports only int
i need a syntax to draw lines across double datatypes ...example, (0.0,0.5)(0.1,0.6)
regards
dhilip

[JosAH]

hi again..
i typed "g.drawLine " on eclipse.. it says the command doesn't support double datatypes, and supports only int
i need a syntax to draw lines across double datatypes ...example, (0.0,0.5)(0.1,0.6)
regards
dhilip

You're trying to draw scaled coordinates so you can safely cast them to type int without any loss of precision.

kind regards,

Jos