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2
votes
3answers
57 views

Referring to the components of a vector within a sum

I feel like I'm missing something obvious here, but.... I'm playing around, trying to do the standard deviation for my stats homework (don't worry, I already worked out the answer by hand), and I ...
-2
votes
1answer
72 views

Recreating in Mathematica a matrix created in Python [closed]

I need to recreate in Mathematica this matrix that I created in Python: ...
1
vote
0answers
33 views

Index change in a recursive definition

Assume I have the following recursive definition: ...
0
votes
1answer
38 views

Finding Coordinates of a Peak on a Pot - Problem with Position[…]

I have plotted a graph from a CSV file which consists of two columns of data Time and Intensity. I simply want to find the time where the intensity is largest. ...
23
votes
7answers
659 views

Faster position list construction from a “take instructions” list

Take some list, e.g., {1,2,3,4,5}, and a "take instructions" list, say {1,1,2,1,1}. The latter is read as "take the first ...
0
votes
1answer
36 views

Recurrence evaluation at specific index

I have the following set of equations. I want to solve a[n] and f[n] for the indices n=1:5. Note that the relation a[2n+2] involves the derivative of f[2n] and the relation for f[2n+2] involves the ...
0
votes
1answer
49 views

Loops over multiple variables (negative i_min)

Can someone explain why i ranges from -3 to 3 in the output of Do[Print[{i, j}], {i, -3, 3}], but not in Do[Print[{i, j}], {i, -3, 3},{j,-i,i}]? I was thinking for the second input I would get ...
0
votes
1answer
85 views

Array element problem in optimization

I have the following piece of code in Mathematica: ...
2
votes
4answers
247 views

How do I find the position of the maximum value in each column of a table?

Given a table of values, I know how to find find maximum values, but how do I find the position of the maximum value in each column. For example, given ...
1
vote
1answer
167 views

Define a Recurrence Table involving other tables

I'm relatively new to using Mathematica. Previously I used Matlab, but lately I noticed that the numbers i got in both of them do not match (mostly it seems that Matlab lacks precision...). The ...
2
votes
0answers
57 views

Unexpected behavior from Indexed

I was going to include Indexed in this answer, thinking that it operated much as a List-only ...
16
votes
4answers
368 views

Make MapIndexed listable

My goal is to apply MapIndexed to every element of a nested list without destroying the arithmetic operations within the elements. For example, let's start with ...
3
votes
1answer
138 views

Collect terms in a sum

Suppose I have this expression ...
8
votes
5answers
410 views

Efficiently finding the positions of a large list of targets in another, even larger list

I have a big list. It contains nearly 60,000 sub-lists. It's structured like bigList = {{x1,y1,z1},{x2,y2,z2},{x3,y3,z3},.....,{x60000,y60000,z60000}}; I have ...