X-Git-Url: http://git.kpe.io/?a=blobdiff_plain;f=math.lisp;fp=math.lisp;h=0197d52d5652a9fcdf28f117a309766fc7f9dc12;hb=e48ac76f4b26ec24080dfaf524482a839cd84fff;hp=be89825d27890bc0e6268a751fe363832662ad18;hpb=7367c68a5daa2ef45c7adf1f4097596f84f5e4dd;p=kmrcl.git

diff --git a/math.lisp b/math.lisp
index be89825..0197d52 100644
--- a/math.lisp
+++ b/math.lisp
@@ -34,3 +34,39 @@
   `(if (stringp ,obj)
       (parse-integer ,obj)
      ,obj))
+
+(defun histogram (v n-bins &key min max)
+  (declare (fixnum n-bins))
+  (when (listp v)
+    (setq v (coerce v 'vector)))
+  (when (zerop (length v))
+    (return-from histogram (values nil nil nil)) )
+  (let ((n (length v))
+	(bins (make-array n-bins :element-type 'integer :initial-element 0))
+	found-min found-max)
+    (declare (fixnum n))
+    (unless (and min max)
+      (setq found-min (aref v 0)
+	    found-max (aref v 0))
+      (loop for i fixnum from 1 to (1- n)
+	  do
+	    (let ((x (aref v i)))
+	      (cond
+	       ((> x found-max)
+		(setq found-max x))
+	       ((< x found-min)
+		(setq found-min x)))))
+      (unless min
+	(setq min found-min))
+      (unless max
+	(setq max found-max)))
+    (let ((width (/ (- max min) n-bins)))
+      (setq width (+ width (* double-float-epsilon width)))
+      (dotimes (i n)
+	(let ((bin (nth-value 0 (truncate (- (aref v i) min) width))))
+	  (declare (fixnum bin))
+	  (when (and (not (minusp bin))
+		     (< bin n-bins))
+	    (incf (aref bins bin))))))
+    (values bins min max)))
+