RE: DO if Loop

*To*: mathgroup at smc.vnet.net*Subject*: [mg26636] RE: [mg26593] DO if Loop*From*: "David Park" <djmp at earthlink.net>*Date*: Sat, 13 Jan 2001 22:36:14 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Bob, A good place for functional programming rather than a Do loop. Here is a short example. list = Table[{Random[Integer, {1, 9}], Random[Integer, {1, 9}], Random[Integer, {1, 9}]}, {5}] {{8, 4, 7}, {7, 6, 7}, {7, 1, 5}, {5, 4, 9}, {3, 1, 8}} For a function, let's say that we want the square root of the sum of squares. If you define the function to operate on a list of three numbers, f[{x_, y_, z_}] := Sqrt[x^2 + y^2 + z^2] then just Map the function onto the elements of the list. f /@ list {Sqrt[129], Sqrt[134], 5*Sqrt[3], Sqrt[122], Sqrt[74]} If your function is defined this way, g[x_, y_, z_] := Sqrt[x^2 + y^2 + z^2] then you have to Apply it to each triplet list and that function is mapped onto the list. g @@ # & /@ list {Sqrt[129], Sqrt[134], 5*Sqrt[3], Sqrt[122], Sqrt[74]} In Version 4, this can be shortened to g @@@ list {Sqrt[129], Sqrt[134], 5*Sqrt[3], Sqrt[122], Sqrt[74]} Check out Map and Apply in Help. David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ > From: Bob Hallam [mailto:pixelpounder at earthlink.net] To: mathgroup at smc.vnet.net > Hello, > > I have a matrix function and a list of 2622 variables in groups of 3. I > need to apply this function to each set of 3 variables continuing until > finished with the list. > > How is this done? > > Best Regards, > > Bob