# Tagged Questions

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

2k views

### How to Derive Tuples Without Replacement

Given a couple of lists like a={1,2,3,4,6} and b={2,3,4,6,9} I can use the built-in Mathematica symbol ...
935 views

### MapThread over sublists of different length

I have a list which looks like this: l={{1,0,3,4},{0,2},{0,0,1,3},{1,2,0}}. Now I would like to count how many 0s the sublists contain in the first, second,... slot....
1k views

### Accessing list elements by name

First, a bit of a long introduction to my problem: I only have a few weeks of Mathematica experience. I am creating a mathematica application that calculates some material properties of steel based ...
1k views

### Selectively Mapping over elements in a List

I am using the following code to easily generate a row of images of all eight planets of our Solar System: ...
2k views

### From a list to a list of rules

Starting from these two lists, var = {a, b, c} values = {{1, 2, 3}, {4, 5, 6}, {7, 8 , 9}} how can I generate a list of rules? ...
7k views

### Is there an equivalent to MATLAB's linspace? [duplicate]

Does Mathematica have an equivalent to Matlab's linspace? I want to make a list with "start", "stop" and "number of points". What is the neatest way of doing this?
514 views

### How to pass a list of arguments into HoldAll

I have a list of arguments (which in reality is lengthy): arguments = {a, b, c} arguments2 = {a_, b_, c_} f[Sequence@@arguments2] := a + b + c Note: It seems ...
1k views

### Checking for duplicates in sublists

I have a list with contains entries that are length 8 sublists,i.e. L1={{a1,b1,c1,d1,A1,B1,C1,D1},{a2,b2,c2,d2,A2,B2,C2,D2},...} and so on. Now, in my problem two ...
10k views

### Mathematica: finding min/max in list

I have a list of coordinates like this one: {{x1,y1},{x2,y2},{x3,y3},...,{xn,yn}} I need to get the minimum and the maximum of all x-values and the minimum and ...
929 views

### Implementing a function which generalizes the merging step in merge sort

One of the key steps in merge sort is the merging step. Given two sorted lists sorted1={2,6,10,13,16,17,19}; sorted2={1,3,4,5,7,8,9,11,12,14,15,18,20}; of ...
390 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 ...
6k views

### Local max/min of Mathematica data sets

Is there a way in Mathematica to find the local maxima of a set of points? Suppose you have ...
347 views

### Drop selection of columns from a ragged array

I have an application where I need to drop some arbitrary list of columns from a ragged array (where of course the shortest array rows have at least all the specified columns). E.g., given a ragged ...
3k views

### Get the coordinates from ContourPlot and RegionPlot

How do I get the coordinates from a contour plot I've done in Mathematica? For example, I have a two-variable function f[x, y], for which I can make a contour plot: ...
2k views

### Selecting a sublist based on Length

If you have a simple list of lists as follows: test = {{1, 2}, {4, 5, 6, 7}, {5, 4, 3}} How do you ask Mathematica to return the sublist of greatest length? I'...
607 views

### Graphically approximating the area under a curve as a sum of rectangular regions

I am completely new to Mathematica. Basically I was trying to write a code to plot a function and draw the approximate area by rectangles. To be more precise, plot a function ...
634 views

### How to use Map inside MapThread?

Given this input lst1 = {{a, b, c}, {d, e, f}}; lst2 = {1, 2}; and the goal is to generate this output ...
2k views

### List manipulation: position & max value combination

Starting with {{0, 0, 0}, {1, 1, 2}, {2, 3, 3}, {3, 4, 5}} I would like to get {{0, 2, 3, 5}, {1, 3, 2, 3}} where the ...
536 views

### Is there a bug in Pick?

I wanted to use the Pick function with a condition. But there seems to be an issue here. Take a look at this: ...
627 views

### Any built-in function to generate successive sublists from a list?

Given lst = {a, b, c, d} I'd like to generate {{a}, {a, b}, {a, b, c}, {a, b, c, d}} but using built-in functions only, ...
880 views

### Delete duplicates in a list, depending on the sequence of numbers

Below, list is a representative sample of my list, which contains lists of integers. I would like to be able to input: ...
2k views

### Ways to compute inner products of tensors

One way to evaluate the following sums is combining Table and Sum: $u_{abcd} = \sum_{e=1}^3 v_{aeb}w_{ced}$ $q_{ab} = \sum_{d,e=1}^3 v_{d e a}w_{deb}$ It will look like ...
474 views

### Element-wise test on List elements

This question could sound pretty silly but I can't find a way to apply element -wise tests to a list. For example if I digit ...
637 views

### Map a function over the columns of an M x N array

I have a $N \times M$ list of lists, or rather, a list of records and I want to map a function over its columns (e.g. find the mean temperature, age, etc.). Map ...
2k views

### Max of a table/list with indeterminate values

Suppose I have a Table: tab = {1., 2., 3., Indeterminate} When I type Max[tab] I get ...
2k views

### Function returning Null along with other unexpected expressions

When I use some function, at the end along with the output I get some NULLs returned that I don't understand the reason for and are highly undesirable. For example, when I define the reversal of list ...
229 views

### Elegant way to partition list to be faster than ParallelTable (using ParallelSubmit), or some alternative?

Suppose you have a function fun[x_] := (Pause[.05*x]; x^2); of which you know that its evaluation time increases with its argument - in this case obviously ...
388 views

### DeleteCases messing with my mind

I'm losing my mind. Please tell me my laptop is doing weird things and not me. Or do I need to get committed someplace? ...
2k views

### How to create functions of arbitrary number of variables? [duplicate]

In the following code what would be the simplest way to generalize it to say some $N_f$ number of $z$ instead of just $z_1$ and $z_2$? ...
1k views

### Tiling a square

I wondered if there was a way to automate the process of finding a way to tile a tile into a square. The idea is to represent the tile with a matrix of $0$s for blank space and $1$s for filled spaces ...
1k views

### Fastest way to check for List membership

I have a set of say 100 numbers {1,3,7,11,19,...3971}. All elements are previously determined. I want to check whether ...
1k views

### Data Table Manipulation in Mathematica: Step 2

In this previous post (Data Table Manipulation in Mathematica) we find the brilliant suggestion proposed by Leonid Shifrin that allows to select specific rows identified by the header name. I'm now ...
2k views

### Simple algorithm to find cycles in edge list

I have the edge list of an undirected graph which consists of disjoint "cycles" only. Example: {{1, 2}, {2, 3}, {3, 4}, {4, 1}, {5, 6}, {6, 7}, {7, 5}} Each ...
532 views

### Distributing elements across a list of lists

I have two lists: u = {{1, 3}, {2, 6}, {3, 9}} v = {0, 4} and I want to obtain this list from them: ...
2k views

### Shuffle product of two lists

I want to do the following: I have two lists {a_1,...a_n}, {b_1,...,b_n} and I would like to build now all shuffles out of this. This means all unions of these ...
617 views

### How can I define a Listable function only apply to a vector?

Consider the function f which should behave as f[{{1, 2}, {3, 4}, {5, 6, 7}}] ...
1k views

### DeleteCases on list of Strings

Consider the following: data={"AB","CD","AF"}; Now I would like to delete all String from data which starts with "A". Result:...
3k views

### Simulate MATLAB's meshgrid function

Here is MATLAB's meshgrid. I came up with these implementations in Mathematica: ...
1k views

### On generalizing Partition[] (with offsets) to sublists of unequal length

The usual Partition[] function is a very handy little thing: ...
470 views

### Quick multiple selections from a list

What is the fastest way to make multiple selections from a list? Compiled methods included. For example, here are two methods for selecting a subset, compared:- ...
846 views

### Vlookup function as Excel in Mathematica

How can we create a Vlookup function, similar to what we have in Excel? So if we have a table a and another b, we could add ...
4k views

### How to get Matlab data imported with the same dimensions?

I have some Matlab image data with the following dimensions (output is from Matlab): >> size(im) ans = 86 86 3 45 The data imports just fine ...
472 views

### Intersection for lists of numeric data

I know that Intersection is a pattern matching function and will not evaluate list elements to determine if two or more list have equal elements. So my question is, ...
3k views

### Is it possible to compute with the trapezoidal rule by numerical integration?

Is it possible to compute trapezoidal rule numerical integration? I know that Mathematica has Interpolation, and that a list of points can be interpolated and then ...
457 views

### Bug in MovingMap (breaking change between version 10.1 and 10.0.2)?

The MovingMap window spec has been changed between version 10.1 and 10.0.2. Version 10.0.2 ...
637 views

### Using MapAt to map at a particular depth (levelspec)

I have the following sample list (my actual list is, of course, much longer): ...
602 views

### Computing the equivalence classes of the symmetric transitive closure of a relation

I have a list of pairs, for example: ...
2k views

### Finding all partitions of a set

I'm looking for straightforward way to find all the partitions of a set. IntegerPartitions seems to provide a useful start. But then things get a bit complicated. ...