add and test helper functions

src/propeller/tools/math.cljc

@@ -107,3 +107,8 @@
   [x]
   #?(:clj  (Math/tan x)
      :cljs (js/Math.tan x)))
+
+(defn transpose
+  "returns a vector containing the transpose of a coll of colls"
+  [x]
+  (apply map vector x))

src/propeller/tools/metrics.cljc

@@ -1,11 +1,26 @@
 (ns propeller.tools.metrics
   (:require [propeller.tools.math :as math]))
 
+(defn argmax
+  "returns the index of the maximum value in a list"
+  [coll]
+  ;(prn {:func :argmax :coll coll})
+  (->> coll
+       (map-indexed vector)
+       (apply max-key second)
+       first))
+
 (defn mean
   "Returns the mean of a collection."
   [coll]
   (if (empty? coll) 0 (math/div (apply + coll) (count coll))))
 
+(defn mean-of-colls
+  "returns the mean of multiple colls"
+  [coll]
+  ;(prn {:func :mean-of-colls :coll coll})
+  (map mean (math/transpose coll)))
+
 (defn median
   "Returns the median of a collection."
   [coll]

src/propeller/utils.cljc

@@ -1,6 +1,21 @@
 (ns propeller.utils
   (:require [clojure.zip :as zip]))
 
+(defn filter-by-index
+  "filters a collection by a list of indices"
+  [coll idxs]
+  ;(prn {:func :filter-by-index :coll coll :idxs idxs})
+  (keep-indexed #(when ((set idxs) %1) %2)
+                coll))
+
+(defn drop-nth
+  "drops the nth element from a collection"
+  [n coll]
+  ;(prn {:func :drop-nth :n n :coll coll})
+  (concat
+   (take n coll)
+   (nthrest coll (inc n))))
+
 (defn first-non-nil
   "Returns the first non-nil values from the collection, or returns `nil` if
   the collection is empty or only contains `nil`."

test/propeller/tools/metrics_test.cljc

@@ -3,6 +3,17 @@
             [propeller.tools.metrics :as m]
             [propeller.tools.math :as a]))
 
+(t/deftest argmax-test
+  (t/is (= (m/argmax '(1 2 3 4))  3))
+  (t/is (= 1 (nth '(1 1 1 1) (m/argmax '(1 1 1 1)))))
+  (t/is (= 3 (nth '(1 3 3 1) (m/argmax '(1 3 3 1)))))
+  (t/is (= 0 (m/argmax '(1)))))
+
+(t/deftest mean-of-colls-test
+  (t/is (= (m/mean-of-colls '((1 2 3 4) (4 3 2 1))) '(2.5 2.5 2.5 2.5)))
+  (t/is (= (m/mean-of-colls '((1 2 3) (4 3 2 1))) '(2.5 2.5 2.5)))
+  (t/is (= (m/mean-of-colls '((1))) '(1.0))))
+
 (t/deftest mean-test
   (t/is (= (m/mean '(1 2 3 4)) 2.5))
   (t/is (= (m/mean '()) 0)))
@@ -15,7 +26,7 @@
 
 (t/deftest levenshtein-distance-test
   (t/is (= (m/levenshtein-distance "kitten" "sipping") 5))
-  (t/is (= (m/levenshtein-distance "" "hello")) 5))
+  (t/is (= (m/levenshtein-distance "" "hello") 5)))
 
 (t/deftest sequence-similarity-test
   (t/is (a/approx= (m/sequence-similarity "kitten" "sipping") 0.2857 0.001))