Re: How Do You Reduce Multiple Elements in a List?

*To*: mathgroup at smc.vnet.net*Subject*: [mg33870] Re: [mg33863] How Do You Reduce Multiple Elements in a List?*From*: SteveC <steve at fractalus.com>*Date*: Sun, 21 Apr 2002 06:12:15 -0400 (EDT)*References*: <200204200649.CAA22326@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

* Bob Harris (nitlion at mindspring.com) wrote: > Given a list of integers that generally contains the same number many times, > I'd like to reduce it to a list that just gives me the number/count pairs. > For example, I'd like to convert the list > {1, 1, 1, 1, 1, 2, 2, 2, 4, 4, 4, 4, 4, 4} > into > {{1,5}, {2,3}, (4,6}} l = {1, 1, 1, 1, 1, 2, 2, 2, 4, 4, 4, 4, 4, 4}; Map[{#, Count[l, #]} &, Union[l]] {{1, 5}, {2, 3}, {4, 6}} or see Statistics`DataManipulation` << Statistics`DataManipulation` Frequencies[l] {{5, 1}, {3, 2}, {6, 4}} ...which returns it the other way around... have fun, SteveC steve at fractalus.com fractalus.com/steve

**References**:**How Do You Reduce Multiple Elements in a List?***From:*Bob Harris <nitlion@mindspring.com>