Assign value to variable
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From: miguelwon on 24 Jul 2010 05:07 Hello. I'm working with some expressions that are dependent of several variables co1, co2, ... , con. I would like to know how can I assign values iteratively to some of these variables. I tried: For[i=1,i<=100,i++, Symbol["co"<>ToString[i]]=0; ]; but it doesn't work. For each iteration it says coi is Protected. Can someone help me? Thanks
From: Bill Rowe on 25 Jul 2010 01:57 On 7/24/10 at 5:07 AM, miguelwon(a)gmail.com (miguelwon) wrote: >I'm working with some expressions that are dependent of several >variables co1, co2, ... , con. I would like to know how can I assign >values iteratively to some of these variables. I tried: >For[i=1,i<=100,i++, Symbol["co"<>ToString[i]]=0; >]; >but it doesn't work. For each iteration it says coi is Protected. >Can someone help me? Assuming the variables you want to assign values to do not have values already assigned to them, then the following will do what you want. In[1]:= Set[Evaluate[ToExpression["c" <> ToString[#]]], #] & /@ Range[5]; {c1, c5} Out[2]= {1,5} This doesn't work if the variables have values assigned to them since the Evaluate will cause the variable to be evaluated to its value resulting in a non-sensical attempt to assign a number to a number.
From: magma on 25 Jul 2010 01:57 On Jul 24, 11:07 am, miguelwon <miguel...(a)gmail.com> wrote: > Hello. > > I'm working with some expressions that are dependent of several > variables co1, co2, ... , con. I would like to know how can I assign > values iteratively to some of these variables. I tried: > > For[i=1,i<=100,i++, > Symbol["co"<>ToString[i]]=0; > ]; > > but it doesn't work. For each iteration it says coi is Protected. > Can someone help me? > > Thanks I would rather use: Table[co[i] = 0, {i, 100}] and would advise you NOT to use co1, co2, etc for indexed variables. Things like co1 and co5 are difficult to manage (for ex. make a list), while things like co[1] and co[5] are very flexible, as you see from my simple Table above. Also: one must be careful what one puts on the LHS of "=". Not everything is accepted. In this case you were trying to give a value to Symbol, which is not possible. Even using Upvalues does not help. Last , but not least,why use For, when you can use Table?
From: James Stein on 25 Jul 2010 01:59 Perhaps something like this? n = 4; (* # of desired variables *) co = Table["co" <> ToString[i], {i, 1, n}]; For[ i = 1, i <= n, i++, co [ [ i ] ] = i ^ 2 ] ; On Sat, Jul 24, 2010 at 2:07 AM, miguelwon <miguelwon(a)gmail.com> wrote: > Hello. > > I'm working with some expressions that are dependent of several > variables co1, co2, ... , con. I would like to know how can I assign > values iteratively to some of these variables. I tried: > > For[i=1,i<=100,i++, > Symbol["co"<>ToString[i]]=0; > ]; > > but it doesn't work. For each iteration it says coi is Protected. > Can someone help me? > > Thanks > >
From: James Stein on 25 Jul 2010 01:59
Big Correction to my preceding post! Tricked by my own cockpit error. Apologies to all. Try this instead: n = 4;(*# of desired variables*) Quiet [ Remove["co*"], Remove::"rmnsm"]; set = Function[#1 = #2]; Table[Symbol["co" <> ToString[ i ] ], {i, 1, n}] For[i = 1, i <= n, i++, set[%[ [ i ] ], i^3] ] {co1, co2, co3} On Sat, Jul 24, 2010 at 4:39 PM, James Stein <mathgroup(a)stein.org> wrote: > Perhaps something like this? > > n = 4; (* # of desired variables *) > co = Table["co" <> ToString[i], {i, 1, n}]; > For[ i = 1, i <= n, i++, co [ [ i ] ] = i ^ 2 ] ; > > > > > On Sat, Jul 24, 2010 at 2:07 AM, miguelwon <miguelwon(a)gmail.com> wrote: > >> Hello. >> >> I'm working with some expressions that are dependent of several >> variables co1, co2, ... , con. I would like to know how can I assign >> values iteratively to some of these variables. I tried: >> >> For[i=1,i<=100,i++, >> Symbol["co"<>ToString[i]]=0; >> ]; >> >> but it doesn't work. For each iteration it says coi is Protected. >> Can someone help me? >> >> Thanks >> >> > |