Create all combinations [x] and [x y] where x,y set's elements (GitHub: csv-statistic)

 (ns clojure.examples.collections
 (:gen-class))
 
(defn alones
[ coll ]

   (for [x coll :when (not (number? x)) ]
    (str ":" x ))
)
 
(defn cartesian-pairs
"Function read col and return list of all possible pairs [ [x1 x2] .. [xi xj] ] alone elements [x] where xi not = xj and xi not number   "
[ coll ]

  (for [x coll  y coll  :when (not= x y) :when (and (not (number? x)) ( not (number? y)))
    :when ( < (.indexOf coll x)  (.indexOf coll y))  ]
   (str ":" x "_" y ))
)
 

(def my-coll [123 45 "b" "f"  "d" "e"  123 1234 4534] )

;(->> my-coll cartesian-pairs println )


(->
(reduce #(assoc %1 %2 (inc (%1 %2 0)))
        {}
        (reduce conj (cartesian-pairs my-coll) (alones my-coll) ))
println
)

The final Result :

{:e 1, :f_d 1, :d 1, :b_d 1, :b_f 1, :f 1, :d_e 1, :f_e 1, :b 1, :b_e 1}     

Let's make small modification and reduce assoc formula will work with atomic collection

  
(def collection (atom {}))
(def my-coll [123 45 "b" "f"  "d" "e"  123 1234 4534] ) 

;(->> my-coll cartesian-pairs println )



(-> 
(reduce #(swap! collection assoc %2 (inc (%1 %2 0)))
        {}
        (reduce conj (cartesian-pairs my-coll) (alones my-coll) ))
println
)

(println "Atomic collection: " @collection)