I'm dipping my toe in graph theory and found that R has a rich collection of network and graph tools. However, I can't seem to put my finger on the solution to my problem. There are several procedures available in R for finding a shortest path along edges between vertices based on the cost of traversing a link, but my problem is to find _all_ of the _longest _paths between vertices for a critical path method-type computation and others in the future. Aside from brute force searching of all possible paths for the longest and piling up a list of those with the same length, can someone point me to a method that's already been figured out? One that I'm trying is to use the inverse of the traversing costs but my first, naive, test gave me the shortest path again. Any thoughts? Regards David -- David K Stevens, P.E., Ph.D., Professor Civil and Environmental Engineering Utah Water Research Laboratory 8200 Old Main Hill Logan, UT 84322-8200 435 797 3229 - voice 435 797 1363 - fax david.stevens@usu.edu [[alternative HTML version deleted]]