Meander experiments with vega

transform.clj

(require '[meander.epsilon :as m])
(require '[meander.strategy.epsilon :as m*])

(def simplify-conjunctions
  (m*/rewrite
   [:and_expr ?x] ?x
   [:or_expr ?x] ?x))

(def simplify-all-conjs
  (m*/bottom-up
   (m*/attempt simplify-conjunctions)))



(defn as-geo [vega-lite-spec]
  (-> vega-lite-spec
      (update :encoding update-keys (fn [k]
                                      (get {:x :latitude
                                            :y :longitude
                                            :x2 :latitude2
                                            :y2 :longitude2}
                                           k k)))
      (assoc :projection {:type :mercator})))


(require '[meander.epsilon :as m])
(require '[meander.strategy.epsilon :as m*])

(def example
  {:data {:url "data/cars.json"},
   :width 400,
   :height 300,
   :background "floralwhite",
   :encoding
   {:x {:field "Horsepower", :type "quantitative"},
    :y {:field "Miles_per_Gallon", :type "quantitative"},
    :color {:field "Origin", :type "nominal"},
    :tooltip
    [{:field "Horsepower", :type "quantitative"}
     {:field "Miles_per_Gallon", :type "quantitative"}]}})

(def cart->lat
  (m*/rewrite
   :x :latitude
   :y :longitidue
   :x2 :latitude2
   :y2 :longitude2))

(def as-geo
  (m*/bottom-up
   (m*/attempt cart->lat)))

{:data {:url "data/cars.json"},
 :width 400,
 :height 300,
 :background "floralwhite",
 :encoding
 {:latitude {:field "Horsepower", :type "quantitative"},
  :longitidue {:field "Miles_per_Gallon", :type "quantitative"},
  :color {:field "Origin", :type "nominal"},
  :tooltip
  [{:field "Horsepower", :type "quantitative"}
   {:field "Miles_per_Gallon", :type "quantitative"}]}}
;;what if we need to point to slightly different fields?

;;convenience wrapper
(defmacro rewriting [& body]
  `(->> (m*/rewrite ~@body) m*/attempt m*/bottom-up))


((rewriting :x :latitude
            :y :longitidue
            :x2 :latitude2
            :y2 :longitude2)
 example)

;;^equivalent to previous answer

;;slightly more complex transforms with arbitrary functions
(let [rename #(update % :field str "-2024")
      f      (rewriting  {:field (m/some ?fld) :as ?m} (m/app rename ?m))]
  (f example))

{:data {:url "data/cars.json"},
 :width 400,
 :height 300,
 :background "floralwhite",
 :encoding
 {:x {:field "Horsepower-2024", :type "quantitative"},
  :y {:field "Miles_per_Gallon-2024", :type "quantitative"},
  :color {:field "Origin-2024", :type "nominal"},
  :tooltip
  [{:field "Horsepower-2024", :type "quantitative"}
   {:field "Miles_per_Gallon-2024", :type "quantitative"}]}}