AM Posted July 20, 2016 Share Posted July 20, 2016 if you want to pick a sample from approx.center (depends on odd/even) of a list... (defun pick-sample-from-center (list span) (let ((center (if (evenp (length list)) (/ (length list) 2) (/ (1+ (length list)) 2))) (span (if (> span (length list)) (length list) (append span)))) (loop repeat span with startpoint = (if (evenp span) (- center (/ span 2)) (- center (/ (1+ span) 2))) for i = startpoint then (incf startpoint) collect (nth i list)))) ;;;EXAMPLES: (pick-sample-from-center '(1 2 3 4 5 4 3 2 1) 7) => (2 3 4 5 4 3 2) (pick-sample-from-center '(1 2 3 4 5 4 3 2 1) 3) => (4 5 4) (pick-sample-from-center '(1 2 3 4 5 4 3 2 1) 6) => (3 4 5 4 3 2) (pick-sample-from-center '(1 2 3 4 5 4 3 2 1) 20) ; (if (> span length) => input-list as output => (1 2 3 4 5 4 3 2 1) lviklund and Stephane Boussuge 2 Quote Link to comment Share on other sites More sharing options...
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