Topic: (Challange) Interpolate

[JohnK]

This challange is to interpolate between two knows situations and return the third unknown value. For instance:

Key -- Value
--------------
20  --  2400
28  --  3200

Find the value for the key 24 and return it to me.

[whdjr]

24 = 2800

[Keith™]

I got my answer ....

[JohnK]

So when do you think we can start posting our solutions? (What did we decide that one time we were talking about submitting lisp to these challanges.)

[Mark]

Well I'd give it a few hours any way.

[Keith™]

dunno ... it is your thread ...

[JohnK]

Okay, a few hours it is then.

Give 'er two hours.

[whdjr]

I thought we said it was up to the original poster of the question.
Hence no directions so I didn't hold back.

[whdjr]

I guess I was too early AND too late.

[JohnK]

lol ...No your lisp. You can post the answer. The  answer is not that hard to achieve.

[SMadsen]

So, you want a linear or a weighed interpolation? What if the values looked like this?

20 -- 2400
28 -- 3200
30 -- 3205

[JohnK]

ummm... yes!



Actualy, I just made mine to handle linear, but if you got one for weighted, thats extra cool!

[Keith™]

Ok ...2 hours are up .....

Code: [Select]

(defun interpolate ( @k1 @v1 @k2 @v2 @N )
  (+ @v1(*(/(- @v2 @v1)(- @k2 @k1))(- @N @k1)))
)


Syntax:
(interpolate Key1 Value1 Key2 Value2 UnknownKey)

[JohnK]

mine too.  ...Wow same one. (Well i guess that was to be expected. Its just a formula after all huh?!)

Code: [Select]

;;;
;;; Example:
;;; 20  --  2400
;;; 28  --  3200
;;; Find the value for: 24
;;; (interpolate 20 2400 28 3200 24)
;;; -> 2800
(defun interpolate (n1 v1 n2 v2 n3)
  (+ (* (/ (- v2 v1) (- n2 n1)) (- n3 n1)) v1))

[whdjr]

hm... no formula here.  Just logic.  24 is halfway between 20 and 28, so 2800 is halfway between 2400 and 3200.