code: public String toJSONString() {
          String parms = DoubleStream.of(parameters)
                  .mapToObj(d -> String.format("%f", d))
                  .collect(Collectors.joining(", ", "[", "]"));
  
          String desc = String.format(format, DoubleStream.of(parameters).mapToObj(Double::valueOf).toArray());
          return String.format(
                  "{name: \"%s\", valid: %s, format: \"%s\", description: \"%s\", parameters: %s, rsquare: %f}",
                  model.getName(), isValid() ? "true" : "false", format, desc, parms, rSquared);
      }
docs: Convert this equation in to a JSON string representing the vital
  statistics of the equation.
  
  @return a JSON interpretation of this equation.