There are many issue with your code, some minors, some majors.
1) minor
if isempty(target) == 1
should be simply
if isempty(target)
isempty returns the logical true or false. Which you then compare to double 1. So matlab has first to convert that logical to double, then compare it. The result of that comparison is then the exact same logical value that isempty returned in the first place.
2) major, and the cause of the error
idx = find((waypoints(:,1) == target(1)) & (waypoints(:,2) == target(2)))
that could be written more neatly as
idx = find(all(waypoints == target, 2));
Either way, that expression will return all the indices of the rows that match target. It seems you assume that there is always just one row. Matlab doesn't assume that, so for matlab idx can be a vector. It can also be empty if there's no match. So yes, later when you use idx to extract rows from waypoints, the result is ?x2.
You can tell matlab to return at most 1 index:
idx = find(all(waypoints == target, 2), 1); %no more than row
but for simulink you may still need to ensure that idx is not empty, maybe (I don't use simulink):
idx = find(all(waypoints == target, 2), 1);
if isempty(idx)
error('something went wrong');
end
%from here on idx is guaranteed to be scalar
3) minor in this context. Major in other context.
In my opinion, length should be deprecated. People misuse it, as you have done here. length returns the size of the largest dimension, luckily for you the largest dimension of waypoints is the number of rows, which is what you actually meant. But wait, until your code is later modifed and more columns added to waypoints. Suddenly your code will stop working. Use numel for vectors, and size with a explicit dimension for matrix, so:
if idx == size(waypoints, 1)
4) major, but goes away once you've solved 2
if idx == scalar
As we saw in 2), idx can be a vector. So you're comparing a vector to a scalar, which will return a logical vector. When you pass a logical vector to if the expression is only true if all the values are true. In your case, if idx is a vector, you are guaranteed that at most one value will be equal to the scalar, so the if will not be true.
5) major,
the idx returned by find may be the last row of waypoints, and you may have added 1 to that in the d2w test, in which case, idx is past the end row of waypoint. Not that if idx is equal to the height, there's no difference between end and idx, so your if test was pointless anyway. Perhaps, you meant:
if idx > size(waypoints, 1)
targetnew = waypoints(end, :);
else
targetnew = waypoints(idx, :);
end
That could be written simpler as:
targetnew = waypoints(min(end, idx), :); %no need for if
