function X=sbitmap(c,K)
% sbitmap - turn sequence of integers into sparse binary bitmap
%
% sbitmap ::
%    Y:[[1,L]->[K]] ~'sequence of L natural numbers in 1..K',
%    K:natural      ~'height of array to return'
% -> X:[[K,L]->0|1] ~'X(i,j)=1 if Y(j)=i'.
%
% See also BITMAP

L=length(c);
if nargin<2, K=max(c); end
X=sparse(c,1:L,1,K,L);
