heatmap.clj

;; calculation function

(defn calc-correlations-matrix [data cols-to-use]
  (doall
   (for [col-1 cols-to-use col-2 cols-to-use]
     {:col-1 col-1
      :col-2 col-2
      :corr
      (Float/valueOf
       (str
        (round
         (fastmath.stats/pearson-correlation (data col-1) (data col-2))
         2 :DOWN)))})))


;; heatmap hanami template         
(def heatmap-chart
  {
   :data :UDATA
   :encoding {:x {:field :col-1 :sort :COLS}
              :y {:field :col-2 :sort :COLS}}
   :height :HEIGHT :width :WIDTH
   :layer [{
            :mark "rect"
            :encoding
            {
             :color {:field :corr :type :quantitative
                     :scale {:scheme "redgrey" :reverse true}}}}

           {:mark "text",
            :encoding
            {:text {:field :corr :type "quantitative"}
             :color
             {:condition {"test"  "datum['corr'] < 0.2"
                          "value" "white"},
              "value" "black"}}}]})

(def simple-data (ds/dataset {:x [1 2 3] :y [4 5 6] :z [9 8 7]}))
(def cols-to-use [:x :y :z])

^kind/vega
(hc/xform
 heatmap-chart
 :HEIGHT 500
 :WIDTH 500
 :COLS cols-to-use
 :UDATA {:values (calc-correlations-matrix simple-data cols-to-use)})