Cannot figure out how to write a formula as input

Question

I am trying to re-write some equation as input in Mathematica, but still cannot get it correctly.

You'll need to define n. You don/t need both Table and Total, because Sum combines those. What is j? Specify yourself an intermediate variable mu43 = ... to simplify your code. Use whitespace to clarify your code. — djp, Mar 21 '15 at 01:24
@belisarius, thanks, you were right. Even the TeX formula was wrongly. Sorry for that. It should be OK now. I also defined "mu" separately, but it is used only once so I thought there was no need to define that, but it look clearer now :). — Johny, Mar 21 '15 at 07:02

ubpdqn · Accepted Answer · 2015-03-21T12:52:01.290

0

Perhaps:

f[r_, t_, n_] := With[{m = (2^(2/3)*(Gamma[7/6]/Gamma[1/2]))^(-3)},
(m n^2 )/(n - 4)Sum
  [Times @@ (Abs[#]^(4/3) & /@ {r[[t, j - 4]], r[[t, j - 2]],r[[t, j]]}),
  {j, 5, n}]]

Testing on rectangular array:

r = RandomReal[{-1, 1}, {5, 10}];
r // MatrixForm
f[r, #, 5] & /@ Range[5]

enter image description here

Ragged array:

test = Join@Table[RandomReal[{-1, 1}, j], {j, 5, 10}]
MapThread[f[test, #1, Length[#2]] &, {Range[Length[test]], test}]

enter image description here

Please check with your own test sample achieves desired result.

edited Mar 21 '15 at 12:52

answered Mar 21 '15 at 11:10

ubpdqn

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Total[Table[...]] == Sum[...] – Dr. belisarius Mar 21 '15 at 12:42
@belisarius will edit...not well...missing point a little too much lately – ubpdqn Mar 21 '15 at 12:51
Trying to shorten it:f1[r_, t_, n_] := With[{m = 1/4 (Gamma[7/6]/Sqrt@Pi)^-3}, m n^2/(n - 4) Sum[ Times @@ Abs@r[[t, j - 4 ;; j ;; 2]]^(4/3), {j, 5, n}]] – Dr. belisarius Mar 21 '15 at 12:57

Cannot figure out how to write a formula as input

1 Answers1