Faster version of find for sorted vectors (MATLAB)

Question

I have code of the following kind in MATLAB:

indices = find([1 2 2 3 3 3 4 5 6 7 7] == 3)

This returns 4,5,6 - the indices of elements in t

Answer 1

Here is a fast implementation using binary search. This file is also available on github

function [b,c]=findInSorted(x,range)
%findInSorted fast binary search replacement for ismember(A,B) for the
%special case where the first input argument is sorted.
%   
%   [a,b] = findInSorted(x,s) returns the range which is equal to s. 
%   r=a:b and r=find(x == s) produce the same result   
%  
%   [a,b] = findInSorted(x,[from,to]) returns the range which is between from and to
%   r=a:b and r=find(x >= from & x <= to) return the same result
%
%   For any sorted list x you can replace
%   [lia] = ismember(x,from:to)
%   with
%   [a,b] = findInSorted(x,[from,to])
%   lia=a:b
%
%   Examples:
%
%       x  = 1:99
%       s  = 42
%       r1 = find(x == s)
%       [a,b] = myFind(x,s)
%       r2 = a:b
%       %r1 and r2 are equal
%
%   See also FIND, ISMEMBER.
%
% Author Daniel Roeske 

A=range(1);
B=range(end);
a=1;
b=numel(x);
c=1;
d=numel(x);
if A<=x(1)
   b=a;
end
if B>=x(end)
    c=d;
end
while (a+1