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11
votes
2answers
207 views

How to correctly implement in a new function the scoping behavior of Table, Sum and other commands that use Block to localize iterators?

It is documented that "Block is automatically used to localize values of iterators in iteration constructs such as Do, Sum, and Table." Therefore the dummy index (iterator) in a Sum is shielded ...
5
votes
2answers
147 views

Cumulative total of columns in a matrix or table

I have the following: matrix1 = {{a, b, c, d}, {e, f, g, h}, {i, j, k, l}, {m, n, o, p}} (Note that it's the data that matters, not the fact it's defined as a ...
4
votes
3answers
806 views

How to speed up large double sums in a table?

I am calculating a 3-by-3 matrix whose elements are given as follows: $$ M_{mn} = \frac{1}{N}\sum_{i=1}^N \sum_{j=1}^N (r^i_m - r^j_m)(r^i_n - r^j_n) \tag{1} $$ where $N$ is the total number of ...
4
votes
1answer
464 views

How to increase the evaluation speed of this somewhat complicated table / matrix operation?

I'd like to calculate the following one-dimensional array: OneDimArray = Table[(Norm[Sum[ MatrixA[[i,j]]VectorB[[j]],{j,N}]])^2,{i,N}] However this takes a very ...
2
votes
5answers
113 views

tabulating summation series with restrictions

Trying to solve this question for a good 5 hours but remained stuck. My intuition tells me I am missing something trivial that I've overlooked or forgotten. I am restricted only to the function 'table'...
1
vote
2answers
43 views

Sum up different arrays into a new array

I have a question regarding sums in arrays. So I have the following array: ...
1
vote
1answer
50 views

Summing results of a table

I have a simple table: example1 = Table[N[x^(x/r), 5], {r, 1, 10}, {x, 1, 10}] I want to create a new table ...
1
vote
1answer
262 views

Summing terms in Table

I have a table that looks like Table[m, {k, 10}, {j, k}, {i, j}] where, m is a square matrix that depends on the indices $i, ...
1
vote
0answers
33 views

Partial Sum of Binary Sequence not Working

I have the following code: ...
0
votes
1answer
108 views

Accessing the elements in a table is slower than calculating each time?

This is a follow-up of How to accelerate combinations and sum calculations here? I have tried all tricks but when N reaches 35 the time is still intimidating in a 16-core server, which is far better ...
0
votes
2answers
91 views

Create and manipulate list with variable length?

Is there a way to create and manipulate a function of a sum of arbitrary length? Specifically, I'd like to create a function like the following: ...
0
votes
1answer
157 views

Follow up: how to evaluate this double sum quickly

This question is a follow-up to my previous question. The code I use at the moment is the following: ...