Questions tagged [map]

Questions about applying functions or operators to expressions, especially constructs that take advantage of Map (/@) functionality.

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41 views

How to change Point options when using Map?

I want to change the point size of the points I am plotting in the code below, but wherever I place the PointSize[] option it doesn't like it. The code is part of a larger program, which generates a ...
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1answer
41 views

loop execution time difference after Map operation

I am box filtering data from a DNS simulation. When filtering the original data read from a file, this is fast. When filtering a function of these data after applying Map, it is 10 times slower. If I ...
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1answer
84 views

Optimal way to evaluate a function over many points

This piggy-backs on my previous question: Parameter space search routine is too fast? I am looking for a fast way to evaluate a symbolic list over many points. So lets say I have a list of symbolic ...
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1answer
36 views

How can I plot various points on a world map and compare distances?

How can I plot various points on a world map and compare distances? For example, the distance between Jerusalem and Westford, MA compared to the distance between Westford, MA and Recife, Brasil? Then ...
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2answers
178 views

Maximum of all distances between any pairs of vertices of a random triangle

Given a set $S_n$ of $n$ points selected uniformly at random in a $d$-ball, I want to estimate the average length of the longest side of a triangle having as vertices any three distinct points of $S_n$...
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1answer
37 views

Replace Table with a fast matrix operation to create for matrices A, B the tensor (b_{ij}A) and similar questions

I have two (nxn)-matrices A=(a_{ij}) and B=(b_{ij}) and I'd like to create the (nxnxnxn)-List C=(b_{ij}*A) so e.g. ...
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3answers
177 views

Nested lamdas: MapThreading a MapAt lambda

Consider a set of (here) 3 series ...
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1answer
74 views

Key-dependent maps preserving association

Suppose I have some association a0 = <| key1 -> val1, ... |> and some function f[key, val]. I'd like to produce the ...
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1answer
26 views

Changing PlotStyle while mapping ListLinePlot at several datasets [closed]

Assume that I have several datasets in a matrix and I want to plot them using ...
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2answers
250 views

How to write a positive function as sum of positive terms only

A multivariate polynomial function can be written in a certain form (x^m (1-x)^n y^k + ... ) if the function is Positive in the whole domain and contains a finite ...
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0answers
50 views

Map Inverse Ordering on Matrix [duplicate]

I have an matrix (symmetric, but any $n \times n$ will do) $$A = \begin{bmatrix} 0 & 4.5 & 6 & 5.5 \\ 4.5 & 0 & 4 & 3 \\ 6 & 4 & 0 & 5 \\ 5.5 & 3 & 5 &...
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1answer
93 views

Plotting conformal mappings: $(x, y) \mapsto (x^2, y)$

I'm currently studying transformation geometry, and I've been trying to figure out a good way to plot conformal mappings on $\mathbb{R}^2$ of the form $$ \mathbf{f} : \pmatrix{x \\ y} \mapsto \pmatrix{...
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3answers
83 views

Multiple Calculations in a condition

I want to add and subtract 3 from a list. pos = {82,84} If[# > 3, (# - 3) && (# + 3)] & /@ pos the output I want: ...
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1answer
76 views

Removing curly brackets in an argument of ArcTan [closed]

I have list of number pairs l = {{1, 0}, {1, 1}, {0, 1}, {-1, 1}, {-1, 0}, {-1, -1}, {0, -1}} of which I want to take the ArcTan ...
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1answer
141 views

Why Does Parallelization Not Speed Up these Seemingly Well-Parallelizable, Simple Functions?

Original Example Consider function f, a parallelized version fPar, and a coarsest-grained parallelized version ...
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2answers
53 views

Map vertex id to vertex coordinate

I want to map vertex labels to vertex coordinates stored in two variables. vl = {6, 9, 12} vd = {{1011, 1127, 420}, {950, 1052, 404}, {780, 1033, 470}} I tried, <...
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2answers
83 views

How to pass arguments and options of a function when using Map?

Suppose I have a list in which I need to map a function to a list. Also suppose that function takes several arguments and even more options (such as styling). How would I pass all arguments and ...
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1answer
60 views

Sort a nested Association by another Association

I have a nested association of numerous pixel values sorted by sample date (e.g. 20190422C) and futher by a strain percentage (e.g. 0, 30, 50). I want to sort it even further using and Association of ...
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1answer
53 views

Crown a list of two sublists with ErrorBar without losing list structure

I have a list with two sublists of numbers, e.g. Sigmaf = {{1,2,3},{3,4,5}}; ... and I would like to crown each number with ...
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1answer
63 views

cascade application of Map or MapThread

In the following application f = MapThread[If [#2 == 0, 0, #1/#2] &, {d, c}] // N; I need to overlay another mapping operation so that ...
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1answer
39 views

Map two input streams, one graphics objects and the other characters through Show

The question is how to sequentially execute Show with two streams of input. The first is graphics object stream and the second is a character stream for supplying ...
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1answer
30 views

sequential execution of Show with two input streams, one of graphics object and another of characters

The question is how to sequentially execute Show with two streams of input. The first is graphics object stream and the second is a character stream for supplying labelling for the graphics. I tried <...
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0answers
52 views

Mapping on changing list

for those who have seen it, I have deleted my previous question, as suggested by @Αλέξανδρος Ζεγγ, The goal : Modifying dynamically the list on which a mapping is done I try to give you a concrete ...
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1answer
16 views

NIntegrate arguments and non-numerical lists

Having two lists a = {1,2,3} b = {4,5,6} and a function f[lo_, hi_] := NIntegrate[x^2, {x, lo, hi}] I would like to ...
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2answers
70 views

Iterate Minimize on a list of functions

I have a function $f$ defined on $[-1,1]$. For a minimal example, it suffices to define f[z_]:=z^2 - 1 I need to find a list of points such that $f(z_0)= f(z_1)$,...
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2answers
66 views

Map of an expression in a 3D grid is very slow

I have a quite large expression as function of $R$, $\phi$ and $Z$ as you can see: ...
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24 views

Optimization of storages capacity

Consider a series of storages where different goods are added into daily. I would like to optimize the distribution of these goods between the storages in a way which takes into account some ...
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1answer
82 views

How do I create a bifurcation diagram for the below iterative map? [closed]

I have tried to create a bifurcation diagram for the following iterative map: x[n+1]=-r Log x[n], x[1]=0.711 and r=1/log(n(n+1)) using the following code But it doesn't work. Any help? ...
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2answers
260 views

Is it possible to speed up this code by eliminating “For” loop?

I am finding how to speed up a code. The code and general equation are as below. ...
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3answers
78 views

Sorting list on multiple criteria based on means of subgroups

I have a set of records where each record is for a particular item. An item is a member of a particular subgroup and a subgroup is a member of a particular group. One item is always a member of a ...
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1answer
88 views

Iterative comparison between different vectors

I have some soccer outcomes for each league round to import in a data form similar to that: ...
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3answers
103 views

Import data from different webpages of the same website

I imported and cleaned the following datasets for england soccer league in order to have home/away rank tables and next round matches: ...
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1answer
54 views

Code a function to obtain an output table from an input dataset taking into account some rules

Good morning, I have an input dataset in the following form: ...
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1answer
49 views

Indexed KeyValueMap

I have been trying to figure it out and I am probably very close, but I have spent 2 hours without sucess. I have the expression below ...
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1answer
48 views
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1answer
56 views

AppendTo inside ParallelMap

I think this question has never been fully answered. In here the problem has already been mentioned, but let me give a MWE. I will solve a given ODE for a wide range of initial conditions and I want ...
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2answers
68 views

WhenEvent with a function

I have the the function kill[x_]:=Map[#->0&,x] which is supposed to set a list of functions to zero. That seems to be working, because ...
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1answer
101 views

Add a legend to a combined Plot

I have trouble adding a second legend to this map (see picture underneath). I need the legend to that show each existing bubble size, with the respective rainbow color (from the map) and with the ...
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0answers
145 views

How to get 3D building data in map functions?

Most modern mapping APIs have 3D model data for city buildings built-in. For example: Is there some way to get this functionality in the Geography related functions? I believe ...
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1answer
227 views

Determining moving ratios over a list

To know how fast values in a list approach 1 I tried #[[1]]/#[[2]] & /@ Partition[{5040, 1460, 280, 76, 16, 2, 1}, 2, 1] This works, but I seek a better ...
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1answer
44 views

How to map a list of entities into a function?

x = RandomChoice[CountryData[]] Here I have defined x to be a random country. ...
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59 views

How to apply command to all elements of a list?

So I generated a list of cities and I want to apply FindGeoLocation to all of them without having to seperate the elements and then applying. ...
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0answers
39 views

Defining a function and order of operations

I feel I have a profound misunderstanding of how Mathematica works. Here's an example that confuses me: Say that for a matrix $A$ I want to extract the first $\mathrm{Tr}(A)$ normalized eigenvectors (...
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3answers
121 views

Function which returns a symbolic jump between two ordinates, e.g. $[f(a,b,c)]^+_- = f(a^+,b^+,c^+)-f(a^-,b^-,c^-)$

I want to create a function in Mathematica which accomplishes the following: $$[f(a,b,c)]^+_- = f(a^+,b^+,c^+)-f(a^-,b^-,c^-)$$ where $f$ is any function (has 3 arguments above but this need not be ...
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1answer
57 views

Concisely operate on RHS of list of rules

I have a length-N list of rules l = {a -> 5, b -> 1, c -> 42} and an length-N vector of scalars... dl = {-1, .2, 5} ...
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168 views

Visualizing the Riemann's mapping theorem [closed]

The Riemann's mapping theorem allows to map any simply-connected domain in the complex plane $\mathbb{C}$ conformal onto the open unit disk. Conformal is meaning preserving angles. This is a complete ...
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1answer
63 views

Why does a list of Iconize objects not work with Map

I am trying to understand how to Map a function onto a list of Iconize objects. Here is a simple example: listOfIconize = Table[ Iconize[Range[10 + i]], {i, 1, 3}] ...
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55 views

Chaining map and abstract functions — when (and why) is parenthesization necessary? [duplicate]

I am a bit confused with how do some expressions in Mathematica get parsed. I was using a combination of map (/@) and abstract functions of the form ...
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16 views

Can I use Postfix with a condition [duplicate]

I have a nested list Data set with mostly numbers, there are a few elements that occur as strings that I want to convert to a number. By postfixing ToExpression I ...
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1answer
46 views

Order or function/list arguments in map/select/others

I keep being uncertain of the correct order of [function,expr] arguments to functions such as Select, Pick, Cases, Position, etc., because I'm used to the ...

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