Re: Partial derviatives in mathematica

*To*: mathgroup at smc.vnet.net*Subject*: [mg95790] Re: Partial derviatives in mathematica*From*: dh <dh at metrohm.com>*Date*: Tue, 27 Jan 2009 06:59:54 -0500 (EST)*References*: <glk1na$los$1@smc.vnet.net>

Hi, I would write input in InputForm not TraditionalForm. A derivative is then written: D[f[x],x] If you later need TraditionalForm, you can get it by wrapping an expression in TraditionalForm[..]. Or reformatting the whole cell. Your problem comes from the fact that PartialD needs a subscript, indicating the variable to differentiate after. hope this helps, Daniel xareon at gmail.com wrote: > Hi all, i got thi Newton-Raphson mathematica code: > > > > Code: > > F[{x_, y_}] = {f1[{x, y}], f2[{x, y}]}; > > jacobian[{x_, y_}] = Transpose[{\[PartialD]x F[{x, y}], \[PartialD]y F > [{x, y}]}]; > > MatrixForm[jacobian[{x, y}]]; > > NewtonSystem[X0_, max_] := Module[{}, > n = 2; > k = 0; > Dp = {0, 0}; > P0 = X0; > F0 = F[P0]; > Print["F[", P0, "]=", N[F0, 3]]; > P1 = P0; > F1 = F0; > While[k < max, > k = k + 1; > P0 = P1; > F0 = F1; > J0 = jacobian[P0]; > det = Det[J0]; > If[det == 0, Dp = {0, 0}, Dp = Inverse[J0].F0]; > P1 = P0 - Dp; > F1 = F[P1]; > Print["F[", P1, "]=", N[F1, 3]];];]; > > > > where f1[x, y] and f2[x, y] are defined in this way > > > > Code: > > f1[{x_, y_}] = n/x - Sum[y*Exp[-y*A*t[i]]*T[i+1], {i, 0, n-1}]; > > f2[{x_, y_}] = n/y - Sum[A*t[i], {i, 0, n-1}] - Sum[x*Exp[-y*A*t[i]]*T > [i+1], {i, 0, n-1}] + Sum[y*x*A*t[i]*Exp[-y*A*t[i]]*T[i+1], {i, 0, > n-1}]; > > > > > T[i] e t[i] are functions defined point-by-point (from T[1] to T[50] > and from t[0] to t[49]) with this syntax: > > > Code: > > t[0] = *un certo numero*; t[1] = *un altro numero*; t[2] = *ancora un > altro numero*; ... T[1] = *numero*; T[2] = *altro numero* ... > > > > I got an error on the second line > > > > Code: > > jacobian[{x_, y_}] = Transpose[{\[PartialD]x F[{x, y}], \[PartialD]y F > [{x, y}]}]; > > > > Mathematica's kernel warns me with this message when i try to insert > it: > > > Code: > > Syntax::sntxf: "jacobian[{x_, y_}] = Transpose[{" cannot be followed > by > "\[PartialD]x F[{x, y}], \[PartialD]y F[{x, y}]}];". > > > > > This line should define a 2-variables function named jacobian, that is > a jacobian matrix. I'm not a Mathematica-guru, but the code should > work anyway. > > What's wrong there? f1 and f2 seem well defined (i.e., when i write > them Mathematica doesn't say nothing bad): > > > > Thank you all ;) >