More troubles coming from indexed variables

*To*: mathgroup at smc.vnet.net*Subject*: [mg25000] More troubles coming from indexed variables*From*: Barbara DaVinci <barbara_79_f at yahoo.it>*Date*: Fri, 1 Sep 2000 01:09:33 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Cari MathGrouppisti Some time ago a post of mine just concerned indexed variables. (I had replies, kind an learned, from many persons - Matthias Bode, David Keith, Steven M. Christensen, Otto Linsuain and Hartmut Wolf. I thank them all.) Now an even worse trouble is running. I'm writing an educational notebook on least-square fit and in a subsection I must show how the well-known formula is carried out. This provides a symbolic data set : datsimx = Table[x[k], {k, 1, 10}] datsimy = datsimx /. x -> y {x[1], x[2], x[3], x[4], x[5], x[6], x[7], x[8], x[9], x[10]} {y[1], y[2], y[3], y[4], y[5], y[6], y[7], y[8], y[9], y[10]} Now I must declare x[1] ... x[10] and y[1] ... y[10] to be costants (otherwise D[] and Dt[] ...) . I tried two ways, both ineffective. (I) ----------------------------------------------------- SetAttributes[SetAttributes, Listable]; SetAttributes[datsimx, Constant]; SetAttributes[datsimy, Constant]; but I get Attributes[datsimx] {Constant} Attributes[datsimx[[1]]] Attributes::ssle: Symbol, string, or HoldPattern[symbol] expected at position 1 in Attributes[datsimx[[1]]] I suppose that is because Head[datsimx[[1]]] x instead of Head[datsimx[[1]]] Symbol Therefore I'm not surprised seeing SetAttributes[#, Constant] & @ datsimx fails too. (II) ----------------------------------------------------- I definded this function f[x_] := ToExpression[ StringJoin[ "Symbol[", ToString[x], "]" ] ] SetAttributes[f, Listable] whose aim is make x[i] "Symbol headed" ("so doing, maybe, SetAttributes stops shouting its warning messages", I deceived myself) But f[datsimx] make me howling with pain again: Symbol::string: String expected at position 1 in Symbol[x[1]]. Symbol::string: String expected at position 1 in Symbol[x[2]]. Symbol::string: String expected at position 1 in Symbol[x[3]]. General::stop: Further output of Symbol::string will be suppressed during this calculation. (This message is rather unclear to me) ------------------------------------------- Please, is there a way to get out alive ? ------------------------------------------- Affettuosi saluti (The above is an Italian idiom meaning something like "yours sincerely") Barbara Da Vinci ______________________________________________________________________ Do You Yahoo!? Il tuo indirizzo gratis e per sempre @yahoo.it su http://mail.yahoo.it