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Mathematica

Vector as an argument in function definition

Al Guy
Posted 11 years ago

Can I somehow specify that G is a vector in function definition so that it won't complain?

c0[G_, \[Theta]0_, \[CapitalPhi]0_, Q_] := 
 Normal@SeriesCoefficient[Sqrt[
   G[[1]]^2  + G[[2]]^2 - 
    2 Q Sin[\[Theta]] (G[[1]] Cos[\[Phi]] + 
       G[[2]] Sin[\[Phi]])], {\[Theta], \[Theta]0, 
    0}, {\[Phi], \[Phi]0, 0}]
POSTED BY: Al Guy
8 Replies
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What function of G do you have in mind? The following works with immediate assignment, but it won't speed up calculations, I am afraid:

f[u_?VectorQ, v_?VectorQ] = u.v

Using vector notation you may write your function a little more elegantly

c02[g_?VectorQ, \[Theta]0_, \[CapitalPhi]0_, Q_] := 
 Normal@SeriesCoefficient[
   Sqrt[g.g - 
     2 Q Sin[\[Theta]] g.{Cos[\[Phi]], 
        Sin[\[Phi]]}], {\[Theta], \[Theta]0, 0}, {\[Phi], \[Phi]0, 0}]

but it only makes sense for a 2-dimensional g, and it only works with delayed assignment. Also, I think SeriesCoefficient does not need Normal.
POSTED BY: Gianluca Gorni
Al Guy
Al Guy
Posted 11 years ago

I was just thinking that if G is multidimensional, say 100, there should be a way to pass it as an argument to a function.

POSTED BY: Al Guy
David Keith
David Keith
Posted 11 years ago
POSTED BY: David Keith
David Keith
David Keith
Posted 11 years ago 
In[17]:= c02[{g1_, g2_}, \[Theta]0_, \[CapitalPhi]0_, Q_] = 
 Normal@SeriesCoefficient[
   Sqrt[g1^2 + g2^2 - 
     2 Q Sin[\[Theta]] (g1 Cos[\[Phi]] + 
        g2 Sin[\[Phi]])], {\[Theta], \[Theta]0, 0}, {\[Phi], \[Phi]0, 
    0}]

Out[17]= Sqrt[g1^2 + g2^2 - 2 g1 Q Cos[\[Phi]0] Sin[\[Theta]0] - 
 2 g2 Q Sin[\[Theta]0] Sin[\[Phi]0]]

In[18]:= c02[{a, b}, c, d, e]

Out[18]= Sqrt[a^2 + b^2 - 2 a e Cos[\[Phi]0] Sin[c] - 
 2 b e Sin[c] Sin[\[Phi]0]]
POSTED BY: David Keith
Al Guy
Al Guy
Posted 11 years ago

You are right, it works with SetDelayed, can we make it work with Set, so that the function will be evaluated right away instead of waiting?

Part::partd: Part specification G[[1]] is longer than depth of object. >>
POSTED BY: Al Guy
David Keith
David Keith
Posted 11 years ago

Could you post an example of a complaint?

In[12]:= c0[G_, \[Theta]0_, \[CapitalPhi]0_, Q_] := 
 Normal@SeriesCoefficient[
   Sqrt[G[[1]]^2 + G[[2]]^2 - 
     2 Q Sin[\[Theta]] (G[[1]] Cos[\[Phi]] + 
        G[[2]] Sin[\[Phi]])], {\[Theta], \[Theta]0, 
    0}, {\[Phi], \[Phi]0, 0}]

In[13]:= c0[{a, b}, c, d, e]

Out[13]= Sqrt[a^2 + b^2 - 2 a e Cos[\[Phi]0] Sin[c] - 
 2 b e Sin[c] Sin[\[Phi]0]]
POSTED BY: David Keith
Al Guy
Al Guy
Posted 11 years ago

Doesn't work.

POSTED BY: Al Guy

You can try with

c0[G_?VectorQ, \[Theta]0_, \[CapitalPhi]0_, Q_]

Beware that using capital letters for variables is not recommended in Mathematica.
POSTED BY: Gianluca Gorni
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