Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.

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8
votes
3answers
171 views

Preserve information in flattening a nested list

I have a series of lists in the form below: list={ {1,1} , {2,2}, {3,{3,1},{3,2},{31,{31,1},{32,2}}} } Its a nested list which the dimension is changing case to ...
8
votes
3answers
147 views

How can I use the overhang argument to Partition to avoid using PadLeft and PadRight here?

Say I have a list of values v = {v1, v2, v3, ... }. I need to partition these values to perform operations with a sliding window (think ...
8
votes
2answers
362 views

Handling vector comparisons in “Piecewise” function

Is it possible for the Piecewise function to process a vector comparison? For example, my input vector is x={0,1,2,3,4} I would like to define a function that ...
8
votes
2answers
485 views

Fluorescence Correlation Spectroscopy Simulation

I am simulating Fluorescence Correlation Spectroscopy which basically involves tracking the random motion of particles in a box with periodic boundary conditions and then calculating their intensity ...
8
votes
2answers
268 views
8
votes
1answer
136 views

Quickly selecting for points in a set that are within a critical distance of points in another set

Imagine two lists of two-dimensional coordinates: listA = RandomReal[{0,100},{202,2}]; listB = RandomReal[{0,100},{97,2}]; I'm attempting to quickly generate a ...
8
votes
4answers
361 views

Best way to modify values in a list of rules?

Recently I had to solve a problem similar to this: Let's say I have a list of list of rules ...
8
votes
2answers
146 views

Behavior of Inner depends on List dimensions?

Consider the following case: ...
8
votes
3answers
238 views

Deleting quasi-duplicates from large list efficiently

I have the need to remove "duplicates" from large (>10K members) lists, where a "duplicate" is either a verbatim duplication, or the element's second entry exists as a first entry for some "earlier" ...
8
votes
2answers
669 views

Rapidly binning 3D data

I have a set of data (about 20 million datapoints for my real data) of the form {x, y, z, m}. There are 3 spatial coordinates x, ...
8
votes
1answer
230 views

Two ways of map a function on the list: Which one is faster?

There are 2 ways to make a function listable on the list: Use Map or use SetAttributes. My question is, which one is faster, ...
8
votes
1answer
153 views

Transformation rule on a list of non-negative integers

I am trying to create a transformation rule that takes a list of non-negative integer values of any length, finds a non-zero entry in the list, adds 1 to all preceding numbers, subtracts 1 from the ...
8
votes
3answers
579 views

Analytically finding critical values in a hysteresis curve made with ListPlot

Let me start with a super basic explanation of what I'm trying to do, and I will follow with a more detailed discussion afterwards. From data in the form shown below (a ...
8
votes
1answer
213 views

Elementwise, compilable min function

I am trying to implement efficiently a transfer-matrix like algorithm. On each iteration, I have two vectors $x=\{x_1,\dots,x_n\}$, $y=\{y_1,\dots,y_n\}$ with real numbers and I need to compute the ...
8
votes
1answer
278 views

How to remove some elements in a list based on a rule?

I want to deal with the following list. mylist = Table[cof[i] exp[i], {i, 1, n}]; (*n is very larege *) exp[ ] is a function ...
7
votes
4answers
428 views

Prepend 0 to sublists

My question is similar to this one, but my goal is to prepend a single 0 the each sublist, not incrementally many 0's. The file I'm working is a CSV containing around 50K sublists of length 35. I've ...
7
votes
6answers
1k views

Simplifying nested If statements

Consider : list = {100,102,103,99,106,107,104,112} I want to consider, extract only the "big moves" of that time series. In this case the moves bigger then 5 ...
7
votes
4answers
477 views

Filter a list generated with Tuples

I generated with Tuples[{{1, 2, 3, 4, 5}, {1, 2, 3, 4, 14}, {1, 2, 3, 4}, {1, 2, 3, 4}, {1, 5, 6, 7, 8}, {5, 6, 7, 8, 10}, {5, 6, 7, 8}, {5, 6, 7, 8}}] ...
7
votes
9answers
383 views

Convert list of lists to cumulative join

I have this: list[1]={1,2,3}; list[2]={7,8,9}; list[3]={15,20,22}; I want this: ...
7
votes
7answers
397 views

How to pick an element of a row corresponding to the minimum in a particular column?

How can I find what value in column 1 of my list corresponds to the minimum value in column 2?
7
votes
5answers
283 views

Making a table with elements like {10i+j, i, j}

Table[10i+j,{i,4},{j,3}] will generate a table that looks like this: {{11,12,13},{21,22,23},{31,32,33},{41,42,43}} I would like ...
7
votes
3answers
697 views

Why don't * and ^ work as I expected on matrices?

For example, this input... {{1, 2}, {3, 4}}*{{1, 2}, {3, 4}} produces this output... {{1, 4}, {9, 16}} and this input... ...
7
votes
3answers
163 views

List has a date and amount, I need to create a cumulative amount by date

I have a list which has a date and a amount, I need to create a list that has the cummulative total with the date. I have the following result: ...
7
votes
6answers
280 views

The locations of (row-wise) minimum elements in a list

I have a list representing a 2D matrix, such as this 3 ⨉ 2 one: {{2.1, 1.01}, {0.01, 7.2}, {7.8, 2.0}} Does anyone know how to find the minimum of each row, ...
7
votes
4answers
248 views

Generate PrimePower counting function

Is there a way to generate a counting function for prime powers - i.e. to create a similar function to PrimePi, but including prime powers. The following will, of ...
7
votes
4answers
403 views

Using MapThread on list of lists

Just a light weight question for learning. If you think this was asked before, please feel free to close it. I am trying to learn MapThread more, and wanted to use ...
7
votes
2answers
215 views

How to generate Intervals from a given list?

If I have a list list={3,7,4,5,1} how to get the List of Intervals /Ranges result = {{1,3},{3,4},{4,5},{5,7}}
7
votes
5answers
169 views

Selecting terms from a matrix

There are similar questions to this on the forum but none fit the purpose here: I would like to extract certain elements of a matrix depending on whether a factor is present or not, and create ...
7
votes
5answers
211 views

Better way to make a certain list with palindromic sublists

Here is my code, which works, but seems a little too long, I think might be a more refined version. ...
7
votes
6answers
184 views

How to join held Lists?

Let's say I have a = Hold@{2+2} b = Hold@{4+4} How can I get Hold@{2+2,4+4} ie join the two held lists ? More ...
7
votes
4answers
457 views

How make f[{x,y}] evaluate as f[x,y]?

I frequently encounter the situation where I have a function of two real variables defined, e.g.: f[x_, y_] := 9 - x^2 - y^2 But then I need to feed into ...
7
votes
4answers
370 views

Find list position and mapping list

Sorry, my English is not very good. I have two lists: ...
7
votes
2answers
239 views

Is there a function which instantly tells you whether an element is part of a list?

I have a very long list of numbers and I want to check whether there's a function (something that would look like PartOfQ[element,list]) that tells you immediately ...
7
votes
3answers
214 views

Numbering nested list according with Depth (or Level)

(This question is slightly similar with Sequentially numbering a nested list, but not exactly the same.) What I want Say I have a nested list ...
7
votes
3answers
391 views

how to efficiently apply function to all pairs of a set (and collect the results)

To build a graph, I need to apply a function f[a_, b_] to all pairs of a list (3500 elements). The function itself returns a link ...
7
votes
4answers
240 views

Evaluating a function using arguments from a sliding window over a list [duplicate]

Possible Duplicate: How to Map a subset of list elements to a function? I want to evaluate a function using arguments from a sliding window over a list. As an example, lets use ...
7
votes
4answers
282 views

Unexpected behavior from GatherBy in version 7

I have come across what appears to be a bug in GatherBy. It appears similar to the problem of using Table[Random[], {1000}] in ...
7
votes
4answers
148 views

Is there a good way to map a function over a list to lists exclusively of a certain depth?

Let's say I have some ragged list. If some elements have some depth $n$, then is there a way I can map a function to only those elements? I.e., for some list foo, ...
7
votes
3answers
397 views

How to create a list of pre-defined functions?

I would like to create a list of Cauchy distribution pdf's, having different locations of their maxima, and being multiplied by different factors; then I'd like to calculate those functions' values ...
7
votes
3answers
462 views

How can I get a running sum for a list?

I've got following data I'm reading from a file: ...
7
votes
4answers
183 views

Button's command is not evaluated in iteration

I wish I didn't feel like a newbie after several months, but... If I enter the following: Table[ Button[ "Number: " <> ToString @ i, Print @ i], {i, 1, 5}] ...
7
votes
4answers
190 views

Generating all matrices with 1 (possibly) replaced by -1

I have a matrix $M$, whose dimension I am unsure of, which has only $\lbrace0,1\rbrace$ entries. I would like to generate all the possible matrices that result from changing (some subset) of the $1$'s ...
7
votes
3answers
363 views

What is the correct way to conditionally add elements to lists? [duplicate]

Possible Duplicate: How to avoid returning a Null if there is no “else” condition in an If contruct I have several situations where I need to conditionally add an element to a list, at ...
7
votes
2answers
317 views

find subsequences of constant increase

A list like l = {0, 1, 2, 3, 4, 5, 7, 9, 12, 13, 18, 19} may have subsequences of constant increase, $a_{n+1} = a_n + k$. For example: ...
7
votes
3answers
437 views

Specifying string patterns in DeleteCases

It seems that DeleteCases is not compatible with string patterns, at least directly (see, for example, this question). Is this true? If so, why is this the case? ...
7
votes
3answers
454 views

Add lists with unequal lengths together to create a matrix

I'm trying to create a stacked bar chart using raw data coming from a MySQL server. The result coming back from one query is: ...
7
votes
5answers
309 views

LengthWhile until first duplication

I have the need to trim each of a large number of potentially very long lists (10^6+ elements) to the length where the last occurrence of any distinct element happens, or said another way, where the ...
7
votes
6answers
223 views

Faster list duplicate 'limiter'

Given some list, e.g., {5, 3, 2, 3, 1, 0, 1, 3, 5, 5, 4, 5, 1, 2, 5, 2, 2, 0, 1, 4}, I need to limit the duplicates, if any, to an arbitrarily chosen number. The ...
7
votes
3answers
245 views

When does a list contain only ones?

I am starting with a list of length n that contains all -1's. For instance, when n = 6 the list is {-1, -1, -1, -1, -1, -1}. I ...