# Questions tagged [map]

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

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135 views

### How to write a duplicate mapping function?

I need a function MapDuplicate that maps a function on all the duplicates in a list. Consider the following list: ...
62 views

### Around with multiple Slots and Map [closed]

I use the following code to produce a list of Around from data: ...
327 views

### Applies f to all locations other than the specified location

MapAt[f, <|"a" -> 1, "b" -> 2, "c" -> 3, "d" -> 4|>, Except["b"]] I want to apply the function <...
244 views

### Enumeration of a nested list

My problem is consisting of following: I have a nested list of following form: {{B, v ** v, b ** B}, {b, B ** b}, {b ** B, v ** v}, {}} And I want to enumerate ...
165 views

### Efficient way to MapApply for Tensor

I need to Map a function with certain arguments $f(\alpha,\beta,\gamma,\delta)$ onto a whole tensor. My current approach looks like ...
1 vote
60 views

### get the first from a list using slots [closed]

Problem. I work with a list and want to get the first element. For specific reasons I want to use # in combination with Map For example ...
89 views

### Map, applying list in a defined function

Suppose I have defined some function (This is arbitrary) F[alpha_,a_,b_,c_]:=List[alpha,a+b+c] I want to apply this F for a given huge list of sets ...
54 views

### How to combine multiple plots via Table when a map is being applied? [closed]

This question is based on this answer ...
47 views

### Creating a heat map in a circle according to positions on x and y axes [duplicate]

I would appreciate advice on writing code. I need to draw a heat map according to positions, it indicates object trajectory so the order is matter. The positions are saved in a nested list. An inner ...
1 vote
49 views

### Comparing performance of ParallelMap with pure function

Test data are here: q = CloudGet[ "https://www.wolframcloud.com/obj/874e3b18-808a-404a-aaa0-4e3ad1ac4668"]; I construct interpolation and an equi-...
21 views

### ParallelMap on TimeSeries not working properly, operations on TimeSeries extremely slow

I have this data: CloudObject["https://www.wolframcloud.com/obj/25f4b06e-2c89-4909-841d-83b7888b6ed8"] which you can get by ...
36 views

### Parallel constructs and automatic kernel starting

The help gives an example on ParallelMap: ParallelMap[(Pause; f[#]) &, {a, b, c, d}] // AbsoluteTiming I tried it and it ...
296 views

### Can I exit a Map over a list of data pairs?

I've written a function, which I intended to Map over lists of some 8,000 element pairs. I created the "toy" code below to illustrate my problem. ...
74 views

### Creating a mesh map with river cross-profiles

I am trying to create a type of 3D mesh map using multiple cross profiles/cross-sections of a river. I have the longitude, latitude, and elevation imported, with two examples shown below: ...
602 views

### How can I "multiply" nested lists?

Given two nested lists alist={{a,b,c},{d,e,f}} blist={{r,s,t},{x,y,z}} How can I get ...
142 views

### Substituting the element of a list into a list that contains the index position

I see similar questions for lists and indexes and manipulating with Thread, MapIndexed,etc., but I do not see how to do a substitution. I have a list of coordinates for a geometric object and a list ...
184 views

### Map function with evaluated and unevaluated parameters

Let's consider a function with evaluated and unevaluated arguments inside: list1 = {1,2,3} list2 = {x,y,z} fun[list_]:={list,ToString@Unevaluated@list} When I use ...
63 views

### Trouble Mapping a Geometric Transformations over a List of different types of Graphics Objects

I am working on some code that allows me to auto-rotate graphics (including ParmetricPlot3D and Plot3D graphics) objects while preserving mouse dragging in a smooth fashion. It works great. The code ...
85 views

### Simplify Map on a list of lists

I have the following example list of matrices: a = {p Table[RandomComplex[], {2}, {2}], q Table[RandomComplex[], {2}, {2}]} where p and q are real variables. I ...
81 views

### MapAt with pure functions

Consider expr = Hold[1 + a + x + b + c + y + z]; idxes = {{1, 3}, {1, 4}}; Q1. I don't understand why ...
1 vote
90 views

### Specify index of array for Map operation

I want to calculate the determinant along the last slice of a 3-dimensional array. So for I do this by slow the Table command. I know that for time reasons I should ...
733 views

### How to create a matrix of paired values from two matrices?

I have two matrices. They are, m1={{a,b},{c,d}}; m2={{w,x},{y,z}}; I want to create a matrix of paired values that looks like this, ...
82 views

### Apply function to specific elements in list [closed]

Say I have a list like myData={{1,m1,v1},{2,m2,v2},{3,m3,v3},{4,m4,v4}}. It could be a dataset, where the first and second variables in each tuple is as desired, ...
186 views

### Converting specific positions of a List into Sublist

Suppose I have a List of numbers: num = Range I want to combine the second and the third element into a sublist to get the result as {1,{2,3},4,5}. I tried ...
141 views

### Complicated double mapping over nested list

I have a list that each term consist of two parts. First part is a graph and second is a list of pairs of vertices that I want to find graph distance of. ...
208 views

### What should mapping over a number or symbol produce?

I expected it to be an error (i.e., produce an error message), but Map[f,num] is num. Why is this the correct behavior? If it is ...
464 views

### How can I create an atomic head or treat some head as atomic during Map?

For example, Map[g, {0, {h[1, 2, 3]}}, {-1}] gives {g, {h[g, g, g]}} I want a ...
92 views

### Mapping Part to a List [closed]

I have a list, x, where each member is itself a list of 2 coordinate points. Sometimes a member is a list of only 1 point, sometimes it is a list of more points. Note that the last member below is a ...
468 views

### How do I map a function pairwise?

Given a list of pairs: data = {{a,b},{c,d},{e,f},{g,h},{i,j}} I need the moving map: MapPair[F,data] ...
571 views

### Maps between finite sets

With SageMath, one can do FiniteSetMaps(["a", "b"], [3, 4, 5]) to get all maps from {a,b} to ...
675 views

### Monitoring Apply / @@@ over large lists

How to monitor and/or print partial progress of Apply, e.g. f @@@ list? I have found answers using Map (e.g. this nice trick using Echo, or this general trick), but ...
890 views

### How can I apply a function only to even-index elements of a list?

A = {1, 2, 3, 4, 5} and, Dd[P_] := P + 1 How can I map "Dd" into "A" such that the outcome is: {1, 3, 3, 5, ...
599 views

### Smart way to remove rules from lists, leaving just values, specifically from FindMinimum output

I would like to know if there is a direct way to remove the rules from a list of rules. I know that, simply, this can be done with: ...
86 views

### Mathematica replaces list of zeros with zero [closed]

Consider the following functions: f[x_]:= {{Im[x], Re[x]}, {Re[x], Im[x]}}; g[x_]:= {{Im[x],0},{0,0}} When applying each of the functions to the list of lists <...
201 views

### How can I do "Map" on a binary function?

If there is a one-variable function, we can f/@{a,b,c} to get {f[a],f[b],f[c]} What to do with it if it comes to a binary ...
141 views

### A Naive Prime Test Implementation - Problem with Table

I tried to write a simple function which implements a naive primality test. ...
451 views

### Map a two argument function to every element on list

I'm new to use the amazing map function in Mathematica, and I've found it really elegant to program in simple lines of code. However, I'd like to perform more elegant stuff. I've found this question, ...
1 vote
100 views

### ReplacementAll with list elements

I'm trying to define a function that replaces certain expressions that appear when calculating scattering amplitudes (not important). Basically, I have a function ...
91 views

### How to use map and slot effectively?

I want to change my code from : f[n_, x_] := n Sin[x ] Table[{x, f[0, x], f[1, x], f[2, x], f[3, x]}, {x, -\[Pi], \[Pi],1.0}] // Chop with OUTPUT : ...
77 views

### Video processing: Efficient way to apply function to pixel time stack (FIJI's Intensity Z-projection)

Starting from a Video, I would like to apply a function f to the stacks of intensity values, over time, for each pixel. In FIJI ...
286 views

### Applying f for a part of list (MapAt is slow)

Suppose that there are 2000 stones in a row. You should grind 1000 of them to make beads. The time loads(making beads) for each stone are similar. But which 1000 stones? case1) the first 1000 stones. ...
36 views

### Private variable issue in a function environnement

I have the following matrix which represents an input from a .txt file. The first column gives the name of the random variable, the second the probability law, the third the parameters related to the ...
60 views

### How to construct a function that picks elements of the kind $\{-1,\{\}\}$?

I am trying to do the following: Given the list {{-1,{}},{2,{1,2}},{-7,{}},{a,{}}}, I am trying to construct a function that throws out all elements with anything ...
53 views

### How to apply a function to the elements of a list with the "L /. x_ ->f[x]" notation? [closed]

Suppose we have a list: {5,6,7} Suppose I have a function like GCD[x,10] and I want to apply it to the given list. I'm trying ...
1 vote
56 views

### How to separately pass elements of a 3D list as part of the arguments of a function

Hi I have a function which its arguments have the form F[a,b,c,d,e] but the 2nd to 4th arguments are in a list of the form R={{{b,c,d},{e,f,g}},{{h,i,j},{k,l,m}}} how can I pass these elements as ...
178 views

### Contour plot with x, y and z values?

I have x , y and z as x = List[1.355, 1.357, 1.359, 1.36, 1.357, 1.355]; and ...
91 views

### Converting 1D map into first order differential equation for bifurcation diagram code

I have existing code to plot bifurcation diagram for coupled first order differential equations. It seems to work for coupled differential equations. To test the code further, I use the simplest ...
34 views

### How to make a manipulatable map that can change color?

I want to color the world map differently according to how much the number of each country. For example, USA using renewable energy for 20% should be colored lighter than Canada using renewable for 50%...
1 vote