Random Select objects from selected group lisp.

Hello,

I need a lisp that would randomly select a certain percentage of objects from an user pre-selected group. We are creating shutters, that are randomly perforated - don't want to manually randomly delete hundreds of small circles.

I've found a lisp from David Bethel (in this forum's archive: http://www.cadtutor.net/forum/archive/index.php/t-52841.html) which works fine, but it would select between all objects in the drawing, even on frozen layers.

The thread is very old so I don't know if Mr. Bethel is still active on this forum.

How would I change this lisp, so that it would first promp me to select objects from which it would then randomly select a certain percentage?

Thanks,

David

Hi there.

I think David is still active, hoping he wont mind.

Here'S what you need. Using the implied "_I" filter instead of "x".

(good example of wanting to highlight a selection set too...)

(defun c:randset (/ ss sl i en el ep pct qty rs)

;;;SMadsen Random Number
(defun randnum (/ modulus multiplier increment random)
 (if (not seed)
     (setq seed (getvar "DATE")))
 (setq modulus    65536
    multiplier    25173
     increment    13849
       seed       (rem (+ (* multiplier seed) increment) modulus)
       random     (/ seed modulus)))

 (cond ((setq ss (ssget "i"))
        (sssetfirst nil nil)
        (setq sl (sslength ss)
               i -1)
        (while (setq en (ssname ss (setq i (1+ i))))
               (setq el (cons en el))))
       (T (alert "\nNo Entities Found")
          (exit)))

 (initget 7)
 (setq pct (getreal "\nPercentage To Randomly Choose:   "))
 (setq qty (fix (* sl pct 0.01)))

 (setq rs (ssadd))
 (while (> qty (sslength rs))
    (setq ep (fix (* sl (randnum)))
          en (nth ep el))
    (if (not (ssmemb en rs))
        (ssadd en rs)))
 
 (sssetfirst nil rs)
 (princ)
)

That will form the selection you need.

Cheers

On 5/2/2017 at 7:15 PM, Jef! said:

Hi there.

 

I think David is still active, hoping he wont mind.

 

Here'S what you need. Using the implied "_I" filter instead of "x".

(good example of wanting to highlight a selection set too...)

 

 

(defun c:randset (/ ss sl i en el ep pct qty rs)

;;;SMadsen Random Number
(defun randnum (/ modulus multiplier increment random)
 (if (not seed)
     (setq seed (getvar "DATE")))
 (setq modulus    65536
    multiplier    25173
     increment    13849
       seed       (rem (+ (* multiplier seed) increment) modulus)
       random     (/ seed modulus)))

 (cond ((setq ss (ssget "i"))
        (sssetfirst nil nil)
        (setq sl (sslength ss)
               i -1)
        (while (setq en (ssname ss (setq i (1+ i))))
               (setq el (cons en el))))
       (T (alert "\nNo Entities Found")
          (exit)))

 (initget 7)
 (setq pct (getreal "\nPercentage To Randomly Choose:   "))
 (setq qty (fix (* sl pct 0.01)))

 (setq rs (ssadd))
 (while (> qty (sslength rs))
    (setq ep (fix (* sl (randnum)))
          en (nth ep el))
    (if (not (ssmemb en rs))
        (ssadd en rs)))
 
 (sssetfirst nil rs)
 (princ)
)

 

 

 

That will form the selection you need.

Cheers

Can this be modified to ask for number of objects to be selected, instead of percentage?

>> Can this be modified to ask for number of objects to be selected, instead of percentage?

Instead of this:

 (setq pct (getreal "\nPercentage To Randomly Choose:   "))
 (setq qty (fix (* sl pct 0.01)))

do this:

(setq qty (geting "\nNumber of items to be selected: "))