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Thread: sine wave in java2D graphics.

Re: sine wave in java2D graphics.
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?
 03042012, 06:00 PM #22
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Re: sine wave in java2D graphics.
The only person who got everything done by Friday was Robinson Crusoe.
 03042012, 06:28 PM #23
 03042012, 06:40 PM #24
 03042012, 06:48 PM #25

Re: sine wave in java2D graphics.
Yes there are FFT libraries out there that are best found via Google.
 03042012, 07:33 PM #27

Re: sine wave in java2D graphics.
 03042012, 08:02 PM #29
 03042012, 08:07 PM #30
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Re: sine wave in java2D graphics.
The only person who got everything done by Friday was Robinson Crusoe.


 03042012, 08:19 PM #33
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Re: sine wave in java2D graphics.
As in "bŭßƨƮǒƤ" 'squire? But then it doesn't even look like "muffin" ...
kindest regards,
JosThe only person who got everything done by Friday was Robinson Crusoe.
 03042012, 08:19 PM #34
Re: sine wave in java2D graphics.
i've done scaling , and dont know ow to plot em next.. heres my coding
Java Code: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,(npts2)/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<npts1; j++) { xs1 = (x[j]xmin)/(xmaxxmin); xs2 = (x[j+1]xmin)/(xmaxxmin); dx = xs2xs1; 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)/(xmaxxmin); 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.PI0);//dmax is 2pi dmin is zero b1[i]=(b[i]0)/(10);//cmax is 1 cmin is zero as[i]=a1[i]*(SXmaxSXmin)+SXmin ; //sxmin,max not set yet,... will set it based on screen values.. bs[i]=b1[i]*(SYmaxSYmin)+SYmin; } }
Last edited by Fubarable; 03042012 at 08:24 PM. Reason: code tags added
 03042012, 09:49 PM #35
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Re: sine wave in java2D graphics.
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':
Java Code:for (int i= 1; i < sx.length; i++) g.drawLine(sx[i1], sy[i1], sx[i], sy[i]);
kind regards,
JosThe only person who got everything done by Friday was Robinson Crusoe.
 03042012, 09:52 PM #36
 03042012, 10:00 PM #37
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 03042012, 10:01 PM #38
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 03062012, 02:27 PM #40
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