//Notes: This isn't beautiful code, but it works. It takes a weights matrix and
//the dimension of the matrix (which could be tested for insteadof passed in). It
//also takes the name of a file. I generated the filename using seconds past midnight
//as a unique timestamp, and then tagged on to that an integer which indicates the
//kth weights .ppm file generated
//Java 1.1 code
//
//Also, the gaussian squashing function is perhaps not the best way to squash
//the weights. Alternate suggestions are happily accepted.

public void printWeightsToFile(double [][] weights, int rows, int cols, String fn) {
    //Prints to stdout the ppm file of selected image (per ppm format in man ppm) 
    FileWriter fw = null;
    PrintWriter pw = null;
    try {
      fw = new FileWriter(fn);
      pw = new PrintWriter(fw);
    } catch (IOException e) {
      System.err.println("IO Exception: " + e);
    }
    String s = "";
    
    s = s +"P3\n";
    s = s +""+ rows + " " + cols + " 256\n";
    s = s +"# Weight space graph autogenerated by PerceptronLearner\n";
    pw.print(s + "\n");
    for (int i=0;i<rows;i++) {
      s="";
      for(int j=0;j<cols;j++) {
	//squash the weights between 0 and 1
	double curr = weights[i][j];
	if (curr>0)	  
	  s = s + "0 " + ((int)(Math.round(256*(2/(1.0 + Math.exp(-2 * Math.abs(curr)))-1)))) + " 0   ";
	else
	  s = s + ((int)(Math.round(256*(2/(1.0 + Math.exp(-2 * Math.abs(curr)))-1)))) + " 0 0  ";
      }
      pw.print(s + "\n");
    }
    pw.close();   
  }
}