CODEWITHSUNDEEP
wolfram-mathematicasum
user1558881
user1558881

Reputation: 225

Summation in Mathematica

I am trying to understand a piece of code I found but I am stuck on this summation. This is part of a larger do loop over n.

UnderoverscriptBox[\(\[Sum]\), \(m = \(-10\)\), \(10\)]\(\(eigenfunctionsort[n, j]\)[\([m + 11]\)] Exp[I*2*\[Pi]*m*x/dp]\)\),{j,1,21}]

What I mainly do not understand is what is happening with the [m+11]. Is that being multiplied with eigen function sort with each step in the sum, or is that simply adding 11 to m at each step in the sum?

Thanks Ben

Upvotes: 0

Views: 398

Answers (1)

High Performance Mark
High Performance Mark

Reputation: 78364

It looks to me as if your expression contains the following sub-expression

eigenfunctionsort[n,j][[m+11]]

which looks as if:

  • there is a call to a function eigenfunctionsort with the arguments n, and j; and
  • the call returns a list of values and the expression [[m+11]] selects the m-plus-11-th element of the list; the doubled square brackets are a short-hand for Mathematica's Part function. Given that m ranges over -10..10 the expression m+11 will range over 1..21.

Upvotes: 1

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