Re: error message
- To: mathgroup at smc.vnet.net
- Subject: [mg5083] Re: error message
- From: rubin at msu.edu (Paul A. Rubin)
- Date: Fri, 25 Oct 1996 22:48:42 -0400
- Organization: Michigan State University
- Sender: owner-wri-mathgroup at wolfram.com
In article <54kal9$d6r at dragonfly.wolfram.com>,
gt1824a at prism.gatech.edu (Heather Mary Hauser) wrote:
->In using FindRoot to find the zeros of a function which I have defined by
a
->procedure (too long to list here), I keep getting the error message
->"FindRoot::frnum:Function{{-0.00004794 - 0.000020387I}} is not a length 1
->list of numbers at {r} = {0.15I}" . r = 0.15I is the first of two values
I
->give to start the search, because I know that there is not a symbolic
->derivative to be found. I also know that this value is near a possible
zero
->because it is midway through an interval where the function changes sign.
->(both real and imaginary parts). Can anybody tell me what this error
message
->means ?
->
->Heather Hauser
->heather at eas.gatech.edu
I can't be 100% certain without seeing the procedure code, but I think the
problem is the nested set braces. FindRoot is substituting .15 I for r in
the function definition and expecting to get back a list containing one
number. (I *think* FindRoot does the substitution using replacement, which
means the function is expected to spit back a number, and replacement
presents it as a list consisting of that number.) The function, however,
is apparently returning a *list* {-0.00004794 - 0.000020387I}, which the
replacement operations surrounds with another pair of braces, thus yielding
a list whose sole entry is a list (containing one number). Check your proc
and see if it isn't making a list out of the answer.
-- Paul
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