Add functions to calc stats

bundle/bundle--stats.el

@@ -0,0 +1,23 @@
+(defun evenp (number)
+  (if (= 0 (% number 2))
+    t
+  nil))
+
+(defun oddp (number)
+  (not (evenp number)))
+
+(defun stats:mean (list)
+  (/ (apply #'+ list) (float (length list))))
+
+(defun stats:median (list)
+  (let* ((sorted (sort (copy-sequence list) #'<))
+         (len (length sorted))
+         (mid (floor (/ len 2))))
+    (if (evenp len)
+        (/ (+ (nth mid sorted) (nth (1- mid) sorted)) 2.0)
+        (nth mid sorted))))
+
+(defun stats:standard-deviation (list)
+  (let ((m (stats:mean list)))
+    (sqrt (/ (seq-reduce (lambda (x acc) (+ x (expt (- x m) 2))) list 0)
+             (length list)))))