Many possible ways...
- Sort a, keep index for b ---
[a,ix]=sort(a); % sort a, keep order index, replace a with sorted vector
b=b(ix); % reorder b to match
plot(a,b) % now are in order on abscissa
2. Use array features instead of separate vectors...
ab=sortrows([a(:) b(:)],1); % combined array of a,b by column sorted by column 1 (a)
plot(ab(:,1),ab(:,1)) % plot the two columns against each other
Any number of permuations of the above are also possible to get to same result including not overwriting the original vectors, doing the sorting "on the fly" in the arguments of the call to plot() instead of making explicit variables, etc., etc., etc., ...
