Given t = {{{-1, -1, -2+2I}, {-1, -1, 3-I}}, {{-1, -1, 4+I}, {-1, -1, -5-5I}}}; how can I extract the imaginary part of the complex elements to obtain {{{-1, -1, 2}, {-1, -1, -1}}, {{-1, -1, 1}, {-1, -1, -5}}}; thank you. Luiz Melo --

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10/20/2010 8:07:25 AM

On Oct 20, 1:07 am, Luiz Melo <luiz.m...@polymtl.ca> wrote: > Given > > t = {{{-1, -1, -2+2I}, {-1, -1, 3-I}}, {{-1, -1, 4+I}, {-1, -1, -5-5I}}}; > > how can I extract the imaginary part of the complex elements to obtain > > {{{-1, -1, 2}, {-1, -1, -1}}, {{-1, -1, 1}, {-1, -1, -5}}}; > > thank you. > > Luiz Melo > > -- t /. u_Complex -> Im[u]

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10/20/2010 9:45:55 AM

Hi Luiz! Luiz Melo wrote: > Given > > t = {{{-1, -1, -2+2I}, {-1, -1, 3-I}}, {{-1, -1, 4+I}, {-1, -1, -5-5I}}}; > > how can I extract the imaginary part of the complex elements to obtain > > {{{-1, -1, 2}, {-1, -1, -1}}, {{-1, -1, 1}, {-1, -1, -5}}}; What about: Function[{e}, If[Im[e] == 0, e, Im[e]], Listable][t] There seems to be no ComplexQ therefore I test with "Im[e] == 0" if it is not a complex number. Cheers, Sebastian

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10/21/2010 11:00:53 AM

Dear all! Luiz was looking for a general solution how to act only on the third component of his vectors. I came up with this: t = {{{-1, -1, -2}, {-1, -1, -3}}, {{-1, -1, -4}, {-1, -1, -5}}}; Map[Apply[Function[{x, y, z}, {x, y, z + a}], #] &, t, {2}] {{{-1, -1, -2 + a}, {-1, -1, -3 + a}}, {{-1, -1, -4 + a}, {-1, -1, -5 + a}}} Here you see that I work only on the third component adding "a". What do you think? Cheers, Sebastian Luiz Melo wrote: > Thanks Sebastian and Valeri for the help. > > I'm actually looking for a function that operates only on the third row of each > column-matrix terms(which happen to be complex in the example I gave), but > leaves the other terms intact. Consider a different example: > > Let > t = {{{-1, -1, -2}, {-1, -1, -3}}, {{-1, -1, -4}, {-1, -1, -5}}}; > > how can I get > > {{{-1, -1, 2}, {-1, -1, 3}}, {{-1, -1, 4}, {-1, -1, 5}}}; > > that is, in this case, I need a function that takes the Abs[] of the 3rd row of > each sub-matrix and leaves the other terms intact. > > Regards, > Luiz > > > >> Hi Luiz! >> >> Luiz Melo wrote: >> > Given >> > >> > t = {{{-1, -1, -2+2I}, {-1, -1, 3-I}}, {{-1, -1, 4+I}, {-1, -1, -5-5I}}}; >> > >> > how can I extract the imaginary part of the complex elements to obtain >> > >> > {{{-1, -1, 2}, {-1, -1, -1}}, {{-1, -1, 1}, {-1, -1, -5}}}; >> >> What about: >> >> Function[{e}, If[Im[e] == 0, e, Im[e]], Listable][t] >> >> There seems to be no ComplexQ therefore I test with "Im[e] == 0" if it >> is not a complex number. >> >> Cheers, >> >> Sebastian >> > > > --

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10/21/2010 11:03:59 AM

t = {{{-1, -1, -2}, {-1, -1, -3}}, {{-1, -1, -4}, {-1, -1, -5}}}; t /. {x_, y_, z_?NumericQ} :> {x, y, Abs[z]} {{{-1, -1, 2}, {-1, -1, 3}}, {{-1, -1, 4}, {-1, -1, 5}}} or Map[MapAt[Abs, #, -1] &, t, {2}] {{{-1, -1, 2}, {-1, -1, 3}}, {{-1, -1, 4}, {-1, -1, 5}}} % == %% True Bob Hanlon ---- Luiz Melo <luiz.melo@polymtl.ca> wrote: ============= Thanks Sebastian and Valeri for the help. I'm actually looking for a function that operates only on the third row of each column-matrix terms(which happen to be complex in the example I gave), but leaves the other terms intact. Consider a different example: Let t = {{{-1, -1, -2}, {-1, -1, -3}}, {{-1, -1, -4}, {-1, -1, -5}}}; how can I get {{{-1, -1, 2}, {-1, -1, 3}}, {{-1, -1, 4}, {-1, -1, 5}}}; that is, in this case, I need a function that takes the Abs[] of the 3rd row of each sub-matrix and leaves the other terms intact. Regards, Luiz > Hi Luiz! > > Luiz Melo wrote: > > Given > > > > t = {{{-1, -1, -2+2I}, {-1, -1, 3-I}}, {{-1, -1, 4+I}, {-1, -1, -5-5I}}}; > > > > how can I extract the imaginary part of the complex elements to obtain > > > > {{{-1, -1, 2}, {-1, -1, -1}}, {{-1, -1, 1}, {-1, -1, -5}}}; > > What about: > > Function[{e}, If[Im[e] == 0, e, Im[e]], Listable][t] > > There seems to be no ComplexQ therefore I test with "Im[e] == 0" if it > is not a complex number. > > Cheers, > > Sebastian >

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10/22/2010 5:37:16 AM

On Oct 21, 2010, at 7:01 AM, Luiz Melo wrote: > > Thanks Sebastian and Valeri for the help. > > I'm actually looking for a function that operates only on the third row of each > column-matrix terms(which happen to be complex in the example I gave), but > leaves the other terms intact. Consider a different example: > > Let > t == {{{-1, -1, -2}, {-1, -1, -3}}, {{-1, -1, -4}, {-1, -1, -5}}}; > > how can I get > > {{{-1, -1, 2}, {-1, -1, 3}}, {{-1, -1, 4}, {-1, -1, 5}}}; > > that is, in this case, I need a function that takes the Abs[] of the 3rd row of > each sub-matrix and leaves the other terms intact. MapAt[Abs, t, Flatten[Table[{i, j, 3}, {i, First[Dimensions[t]]}, {j, Dimensions[t][[2]]}], 1]] More generally mapAtColumn[t_,column_,f_]:==Module[{d},MapAt[f,t,Flatten[Table[Append[Table[d[i],{i,ArrayDepth[t]-1}],column],Evaluate[Sequence@@Table[{d[i], Dimensions[t][[i]]},{i,ArrayDepth[t]-1}]]],ArrayDepth[t-2]]]] will map f onto the last position column of a multidimensional array t. This can be further generalized to map onto a single value of a particular dimension and all other dimensional values. Regards, Ssezi >> Hi Luiz! >> >> Luiz Melo wrote: >>> Given >>> >>> t == {{{-1, -1, -2+2I}, {-1, -1, 3-I}}, {{-1, -1, 4+I}, {-1, -1, -5-5I}}}; >>> >>> how can I extract the imaginary part of the complex elements to obtain >>> >>> {{{-1, -1, 2}, {-1, -1, -1}}, {{-1, -1, 1}, {-1, -1, -5}}}; >> >> What about: >> >> Function[{e}, If[Im[e] ==== 0, e, Im[e]], Listable][t] >> >> There seems to be no ComplexQ therefore I test with "Im[e] ==== 0" if it >> is not a complex number. >> >> Cheers, >> >> Sebastian >> > > > -- > >

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10/22/2010 5:38:33 AM