stat.ps

% PostScript Statistics Procedures
% by Raymond Luckhurst, scriptit.uk

% constants
/MADK 1.4826 def % median absolute deviation consistency constant for normal distribution

% calc mean
% <sample> mean <mean>
/mean {
	0 % sum
	0 1 3 index length 1 sub {
		2 index exch get add
	} for % each value
	exch length div % mean
} bind def

% calc median
% <sorted sample> median <median>
/median {
	dup length 1 sub 2 div
	dup floor cvi
	exch ceiling cvi
	2 copy eq {
		pop get
	}{
		2 index exch get
		3 1 roll get
		add 2 div
	} ifelse
} bind def

% calc median absolute deviation
% <sample> <median> mad <mad>
/mad {
	1 index length array
	0 1 4 index length 1 sub {
		dup 4 index exch get 3 index sub abs 2 index 3 1 roll put
	} for % each value
	3 1 roll pop pop
	{} insertionsort % sort
	median
	//MADK mul
} bind def

% calc standard deviation
% <sample> <mean> sd <sd>
/sd {
	1 index length 1 sub
	dup 0 ne {
		0 % sum
		0 1 3 index {
			4 index exch get 3 index sub dup mul add
		} for % each value
		exch div sqrt % sd
		exch pop exch pop
	}{
		pop pop pop
		0
	} ifelse
} bind def