boolean init_functions() {
   GenericDialog gd = new GenericDialog("Fitting Options");
   gd.addStringField("Extra Definitions", exdef, 50);
   gd.addCheckbox("Weight Using Plot Errors", false);
   gd.addStringField("Weighting Equation (y is for data)", weightfunction, 50);
   gd.addStringField("Fit_Equation", function, 50);
   gd.showDialog();
   if (gd.wasCanceled()) {
     return false;
   }
   exdef = gd.getNextString();
   boolean errweights = gd.getNextBoolean();
   weightfunction = gd.getNextString();
   function = gd.getNextString();
   // first initialize the weights
   weights = new float[tempdata.length];
   if (errweights
       || weightfunction.equals("")
       || weightfunction == null
       || weightfunction == "1.0") {
     if (errweights) {
       for (int i = 0; i < tempdata.length; i++) weights[i] = 1.0f / (errs[i] * errs[i]);
     } else {
       for (int i = 0; i < tempdata.length; i++) weights[i] = 1.0f;
     }
   } else {
     for (int i = 0; i < tempdata.length; i++) {
       String script =
           "y =" + tempdata[i] + "; " + "x =" + tempx[i] + "; " + "retval=" + weightfunction + ";";
       Double temp = new Double(0.0);
       try {
         temp = (Double) engine.eval(script);
       } catch (Exception e) {
         IJ.log(e.getMessage());
       }
       if (!(temp.isInfinite() || temp.isNaN())) {
         weights[i] = temp.floatValue();
       }
     }
   }
   // now compile the function script
   try {
     String script1 = exdef + "; retval=" + function + ";";
     cs = ce.compile(script1);
   } catch (Exception e) {
     IJ.log(e.toString());
     return false;
   }
   return true;
 }