Add functions to make a frequency map.

src/cipher_analytical_machine/analyzers/analyzers.clj

@@ -36,3 +36,22 @@
             0
             letter-counts)))
 
+(defn sort-map-by-count
+  "Return a list of pairs from a map of pairs where a pair is a character and its count. The order is descending."
+  [count-map]
+  (->> count-map
+       (reduce (fn [acc [char count]] (conj acc [char count])) [])
+       (sort-by #(- (second %)))))
+
+(defn table-to-string
+  "Return the string from a frequency table."
+  [table]
+  (->> (map first table)
+       (apply str)))
+
+(defn symbol-frequency-table
+  "Return a table where pairs is a symbol from a cipher text and its value which is a symbol from frequency table."
+  [cipher-table frequency-table]
+  (zipmap (table-to-string (sort-map-by-count cipher-table))
+          (table-to-string (sort-map-by-count frequency-table))))
+

test/cipher_analytical_machine/analyzers/analyzers_test.clj

@@ -0,0 +1,40 @@
+(ns cipher-analytical-machine.analyzers.analyzers-test
+  (:require
+   [clojure.test :refer :all]
+   [cipher-analytical-machine.analyzers.analyzers :refer :all]))
+
+(deftest count-characters-test
+  (testing "Count two dublicates and one uniq character from a string."
+    (is (= {\a 2 \b 1}
+           (count-characters "aba")))))
+
+(deftest chi-squared-letter-statistic-test
+  (testing "If the frequence of A is 0.1, the text length is 100 and contains 20 times, then the chi-squared is 10."
+    (is (= 10.0
+           (chi-squared-letter-statistic 20 0.1 100))))
+
+  (testing "If the frequence of A is 0.1, the text length is 10 and contains 5 times, then the chi-squared is 16.0."
+    (is (= 16.0
+           (chi-squared-letter-statistic 5 0.1 10)))))
+
+(deftest chi-squared-statistic-test
+  (let [text "aaaaabbbbb"]
+  (testing "If the frequencies of a and b is 0.1, the text length is 10 and contains them 5 times, then score is 32."
+    (is (= 32.0
+           (chi-squared-statistic text {\a 0.1 \b 0.1}))))))
+
+(deftest sort-map-by-count-test
+  (testing "Test the sort in descending order."
+    (is (= [[\b 3] [\a 2] [\c 1]]
+           (sort-map-by-count {\a 2 \b 3 \c 1} )))))
+
+(deftest table-to-string-test
+  (testing "Test the sort in descending order."
+    (is (= "bac"
+           (table-to-string [[\b 3] [\a 2] [\c 1]])))))
+
+(deftest symbol-frequency-table-test
+  (testing "Test the sort in descending order."
+    (is (= {\d \b, \e \a, \f \c}
+           (symbol-frequency-table {\d 3 \e 2 \f 1} {\b 3 \a 2 \c 1})))))
+