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Questions tagged [gathering]

Questions on gathering, grouping or clustering data based on certain criteria. This is to be used with primary tags such as list-manipulation, string-manipulation or similar tags, with the primary tag indicating the specific use case.

1
vote
1answer
22 views

Merging values of a list of rules where some keys occur more than once

I have a list of rules resembling rules = {{a -> {1, 2, 3}}, {b -> {2, 3, 4}}, {c -> {3, 4, 5}, c -> {4, 5, 6}}} How can I neatly rearrange this to ...
2
votes
2answers
56 views

Median of multiple lists of points

I have three lists of points that I want to combine, take the median of and then plot. I'm not entirely certain how to combine and median them. They are data points from three different months, and ...
2
votes
1answer
393 views

Converting built-in Mathematica symbol to C [closed]

I am trying to convert my Mathematica code to C since it can sometimes takes the Mathematica code quite a while to execute since the arrival times lists are hundreds of thousands of counts long, and ...
1
vote
1answer
112 views

How do I access individual groups after using GroupBy on a Dataset object?

I want to read in an xlsx (Excel) or TSV (tab-delimited) file, assuming this results in a rectangular table of data. Then I after applying GroupBy (using multiple keys), I should have several ...
4
votes
2answers
51 views

Groupings of the Elements of a List with at Most $k$ Elements

Given a list with $n$ elements and an integer $k$ I want to get a list with all possible groupings of these n elements in sets with at most k elements. For example, given $n=\{1,2,3,4\}$ and $k=3$ I ...
2
votes
1answer
36 views

Attempting to fill a table with the number of elements in each bin and make a table with the elements in the bins?

I am having some difficulty trying to fill a table with the number of elements in each bin while also making a table that holds the elements in each bin. Okay, let me go over my thoughts: So I have ...
1
vote
1answer
42 views

GatherBy first entry of data

Assume I have data(sim) below. How can I extract first point on each horizontal line? ...
6
votes
2answers
131 views

Creating lists within lists by sorting

I've been working with lists and am stuck on creating lists within a list based on the first element within that list. So for instance, if I have the list: ...
5
votes
0answers
49 views

Speeding up Gather / DatePlus combination

I am working on a project that involves identifying runs of dates that fall within five business days of each other. Given a list of dates in inDates, the following ...
11
votes
3answers
201 views

Convert association with list key to nested assocations

I have an association that maps {x, y} pairs to values, for example: ...
7
votes
4answers
254 views

Group by Lengths of Lists [duplicate]

Let’s say, we have a list of lists: Table[0, {30}, RandomInteger[{1, 5}]] which might look like this ...
4
votes
1answer
31 views

Merge associations always taking the value that satisfies a given test

I have associations look like this: data = {<|a -> {2, l1}, b -> {3, l1}|>, <|a -> {3, l2}, b -> {2, l2}|>} I want the result: ...
5
votes
5answers
305 views

Taking the weighted mean of parts of a list using another list

I have three lists: data = {1,0,0,0,1,0,1,0}; time = {1,1,1,1,4,4,4,4}; weight = {0.5,0.5,0.5,0.3,0.5,0.6,0.7,0.8}; data ...
5
votes
2answers
78 views

On GroupBy's *red* argument in nested groupings

The documentation for GroupBy includes the following cases, among others: ...
7
votes
6answers
145 views

Replace a set of vectors in a list from another set of vectors

I have lists A = {{0,0.1,50,"A"},{200,0.2,120,"E"},{300,0.32,500,"G"},{400,0.33,800,"GO"}} B={{0,0.1,821,"new1"},{310,0.32,911,"new"}} I need to modify ...
3
votes
3answers
523 views

Split list based on positions contained in another list

The problem Suppose that after importing several files into my nb (x-y dataset, but this procedure should work also for x-y-z datasets), I end up with a nested list similar to: ...
2
votes
1answer
56 views

Gather element of a list based on their head

I have list of the form {y[-1], y[0], w'[1], y'[0], w'''[-1], z''[-1]} and I would like to gather the elements together based on their heads to have ...
1
vote
1answer
115 views

Creating 2 separate table from a table using a condition

I want to make two List/Table(B,C) to separate my values from an existing table(A). To illustrate my question, there is my code: ...
8
votes
5answers
172 views

Components rules from ArrayComponents

What is the most efficient way to get component rules from ArrayComponents, so additionaly to data = {"a", "b", "a"}; cmp = ArrayComponents[data] ...
0
votes
1answer
100 views

How do you group cycles?

I want to define a function that takes a list of pairs as input and groups cycles, e.g. {{a1,a2},{b1,b2},{a2,a3},{c1,c2},{a3,a1},{b2,b1}} becomes ...
2
votes
1answer
59 views

Partition lists into sub-lists based on whether they are consecutive or not [duplicate]

I am new to Mathematica and would appreciate any help. I'd like to partition my data which is comprised of {time x analog input} into sublists of consecutive time. In other words, my data looks like ...
4
votes
0answers
105 views

Dataset row position changed by GroupBy in 11.0.1

Bug introduced in 11.0.0 and persisting through 11.0.1 or later In 10.4.1 and previous versions then using GroupBy in a Dataset ...
1
vote
1answer
90 views

Group list by rules in sequence using DateDifference and Total

I have a list and would like to group it into sublists using a couple rules. First rule: the date difference between sequential elements is less than 3. Second Rule: the total of the second ...
2
votes
1answer
72 views

Table from grouping an association by value

I have an Association with lots of key-value pairs. The values are integer numbers from a finite set. I'd like to group all the keys that have a certain number as value, and make a table with values (...
3
votes
2answers
87 views
1
vote
1answer
156 views

How to merge some sublists in a very large list ?

I simplified my problem as follows, ...
6
votes
3answers
281 views

Split list when there is an empty row

I am trying to split a list when there is an empty row. I have tried the following: a = {{1, 1, 1}, {2, 2, 2}, {, ,}, {3, 3, 3}}; b = Split[a, # == Null] but my ...
13
votes
3answers
358 views

Dataset collapsing/reducing

I have a dataset ds with 3 columns named A, B, C. Columns A and B have repeated values. How can I obtain another dataset that contains a list of the values in C for ...
2
votes
3answers
195 views

binning list of lists in unequal bin lengths

I'm lookin for binning of ...
1
vote
2answers
177 views

Group matrix values by column [closed]

Original Question: I have a list {{a, 1}, {b, 3}, {c, 1}, {d, 2}, {e, 3}}. I want to be able to group the the first number in each pair that has the same second ...
2
votes
2answers
191 views

Group Datasets and take minimum/maximum

Good Morning I have the following dataset: And I try to reach this output: key: only one row per key text: join all texts of the rows with the same key (but no duplicates) min: take the lowest ...
1
vote
2answers
215 views

Creating Association [duplicate]

I have provided a dataset bellow and I would like to store the data as an Association that I can query. Such that e.g. ...
3
votes
2answers
179 views

Problem with Custom Sort/Split/Gather

Please help me Sort/Split/Gather/Group(by) a set of symbolic expressions! (extreme TL;DR at bottom) I have a set of symbols (which represent 2-vectors in a plane, ultimately) and I want to sort/...
15
votes
6answers
649 views

Reshaping associations, generalization of GroupBy

Let's say we have a set a\of associations: ...
3
votes
2answers
117 views

Role of Accuracy in numerical evaluations, SplitBy vs GatherBy

This is a follow-up question to this question. I generated a list by substituting the results of a solve[] routine and set: ...
19
votes
4answers
659 views

Partition on sublists beginning with a certain marker elements

Say I have the list {{a}, {0, 2, 5}, {5, 4, 1}, {a}, {1, 1, 0}, {1, 4, 2}, {3, 3, 0}, {a}, {3, 2, 0}, {1, 4, 1}} I would like to make sublists of everything ...
11
votes
3answers
242 views

Grouping by total length of elements grouped

How might one split a list of irregularly-long sublists into groups, each of which is shorter than a specified length? For example, given the following input: ...
32
votes
4answers
828 views

How to organically merge nested associations?

Suppose I want to construct an association of associations, such as a list of people with attributes: ...
34
votes
2answers
730 views

GroupBy twice gives different results

Bug introduced in 7.0 or earlier and persisting through 11.1 It took me quite a lot of time to finally trace down to this strange output. I really don't know why. First, I create a list ...
6
votes
3answers
152 views

Grouping words by their differences

I'm a new guy here and I face a problem. I should pair the following words according to the rule: pair the words, that differ by max. 2 characters, like: ...
7
votes
2answers
383 views

Exception with GatherBy: gathering complex conjugates

I want to gather the complex-conjugates that are in a list, but with an exception: only if the imaginary part isn't zero. For example: ...
7
votes
2answers
213 views

Allocate amount A according to the distribution of amount B

I have a cost that varies by category and date. I also have the counts of each item type within each category and date. I want to distribute the cost to each of the item types. I'm trying to use <...
7
votes
2answers
219 views

Grouping the list of numbers that have common.

I am working on some simple problem. It is like puzzle.. Let's say I have some list input={{1,1},{1,2},{1,3},{2,3},{3,3},{4,4}} Which means 1 can go and back to ...
2
votes
3answers
257 views

Join nested lists based on first and last elements within each list

I have a nested list like this: test1 = {{1, 3}, {1, 4}, {1, 7}, {2, 1}, {3, 5}, {4, 1}, {5, 2}, {6, 1}, {7, 6}} I want to join the lists together depending on ...
1
vote
4answers
121 views

GatherBy output with given Shape

I would like to group items in a binary list according to some property like in the following simple example. ...
11
votes
4answers
407 views

Handy / flexible directory tree operations

Is there any shorter / more handy / more flexible way to get directory tree as a nested Rules/Associations list? I tried to incorporate ...
4
votes
2answers
192 views

Using GatherBy with a DataSet's header designation instead of First

Using the code, where ds is data formatted into a Dataset GroupBy[ds, First] // TableForm I get a table that I wanted, but I was wondering if I could somehow use ...
2
votes
5answers
225 views

GatherBy based on condition imposed on index variable

Excuse me. This might be user specific question but I need your help. I have an indexed data, where positive integers are used for indexing data. I am trying to group data putting condition on index ...
4
votes
2answers
192 views

How to sum values in the list that belongs to same week

I need to sum values that belongs to same week. For example, I have the list x with one column and n rows. Format: ...
4
votes
3answers
935 views

Partitioning time series

I have a time series dataset I'm trying to plot by Year: ...