[newx, info] = pgfplot_merge(x1, x2);
The pgfplot_merge() function merges two vectors. The
arguments x1 and x2 are increasing vectors. The
resulting column vector newx contains each element from
x1 and x2 once (a number contained in both x1
and x2 appears only once in newx).
The info result is a vector of same size as newx containing boolean values corresponding to the values in newx. The value is true for newx elements obtained from the x2 vector.