(defmacro heat-map
"
  Examples:
    (use '(incanter core charts))
    (defn f [x y] (sin (sqrt (plus (sq x) (sq y)))))
    (view (heat-map f -10 10 -15 15))
    (view (heat-map f -10 10 -10 10 :color? false))

    (defn f2 [x y] (plus (sq x) (sq y)))
    (view (heat-map f2 -10 10 -10 10))
    (view (heat-map f2 -10 10 -10 10 :color? false))

    (use 'incanter.stats)
    (defn f3 [x y] (pdf-normal (sqrt (plus (sq x) (sq y)))))
    (view (heat-map f3 -3 3 -3 3 :x-label \"x1\" :y-label \"x2\" :z-label \"pdf\"))
    (view (heat-map f3 -3 3 -3 3 :color? false))

    (defn f4 [x y] (minus (sq x) (sq y)))
    (view (heat-map f4 -10 10 -10 10))
    (view (heat-map f4 -10 10 -10 10 :color? false))


    (use '(incanter core stats charts))
    (let [data [[0 5 1 2] 
  	          [0 10 1.9 1] 
	          [15 0 0.5 1.5] 
	          [18 10 4.5 2.1]] 
          diffusion (fn [x y] 
	  	      (sum (map #(pdf-normal (euclidean-distance [x y] (take 2 %)) 
                                             :mean (nth % 2) :sd (last %)) 
			        data)))]
      (view (heat-map diffusion -5 20 -5 20)))

"
  ([function x-min x-max y-min y-max & options]
    `(let [opts# ~(when options (apply assoc {} options))
           x-lab# (or (:x-label opts#) (format "%s < x < %s" '~x-min '~x-max))
	   y-lab# (or (:y-label opts#) (format "%s < y < %s" '~y-min '~y-max))
           z-lab# (or (:z-label opts#) (str '~function))
           args# (concat [~function ~x-min ~x-max ~y-min ~y-max] 
			 (apply concat (seq (apply assoc opts# 
						   [:z-label z-lab#
						    :x-label x-lab# 
						    :y-label y-lab#]))))]
       (apply heat-map* args#))))