Questions tagged [map]
Questions about applying functions or operators to expressions, especially constructs that take advantage of Map (/@) functionality.
397
questions
6
votes
10
answers
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:
...
- 9,033
0
votes
0
answers
62
views
Around with multiple Slots and Map [closed]
I use the following code to produce a list of Around from data:
...
- 560
5
votes
4
answers
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 <...
- 26.1k
4
votes
2
answers
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 ...
- 67
2
votes
1
answer
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
...
- 122
1
vote
0
answers
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
...
- 2,585
2
votes
2
answers
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
...
- 801
0
votes
1
answer
54
views
How to combine multiple plots via Table when a map is being applied? [closed]
This question is based on this answer
...
- 899
0
votes
0
answers
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 ...
- 297
1
vote
0
answers
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-...
- 3,703
0
votes
0
answers
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
...
- 3,703
0
votes
0
answers
36
views
Parallel constructs and automatic kernel starting
The help gives an example on ParallelMap:
ParallelMap[(Pause[1]; f[#]) &, {a, b, c, d}] // AbsoluteTiming
I tried it and it ...
- 3,703
5
votes
2
answers
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.
...
- 14.3k
3
votes
0
answers
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:
...
8
votes
4
answers
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
...
- 737
5
votes
3
answers
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 ...
- 55
7
votes
2
answers
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 ...
- 392
3
votes
1
answer
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 ...
- 5,377
2
votes
1
answer
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 ...
- 957
3
votes
1
answer
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
...
- 572
1
vote
2
answers
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 ...
- 654
8
votes
6
answers
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,
...
- 91
3
votes
2
answers
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, ...
- 143
4
votes
5
answers
186
views
Converting specific positions of a List into Sublist
Suppose I have a List of numbers:
num = Range[5]
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 ...
- 899
5
votes
3
answers
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.
...
- 7,044
4
votes
2
answers
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 ...
- 13.5k
11
votes
2
answers
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[0], {h[g[1], g[2], g[3]]}}
I want a ...
- 16.9k
2
votes
2
answers
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 ...
- 347
7
votes
3
answers
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]
...
- 19.5k
5
votes
2
answers
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 ...
- 395
14
votes
4
answers
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 ...
- 243
6
votes
5
answers
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, ...
- 61
7
votes
5
answers
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:
...
- 673
4
votes
1
answer
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 <...
- 255
7
votes
1
answer
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 ...
- 337
5
votes
1
answer
141
views
A Naive Prime Test Implementation - Problem with Table
I tried to write a simple function which implements a naive primality test.
...
- 153
5
votes
2
answers
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, ...
- 673
1
vote
1
answer
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 ...
- 239
0
votes
1
answer
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 :
...
- 1,502
3
votes
0
answers
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 ...
- 35.8k
3
votes
4
answers
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.
...
- 4,037
0
votes
1
answer
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 ...
- 466
0
votes
2
answers
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 ...
- 5,121
0
votes
2
answers
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 ...
- 5,121
1
vote
1
answer
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 ...
- 370
0
votes
1
answer
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
...
- 811
0
votes
0
answers
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 ...
- 883
0
votes
0
answers
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
0
answers
77
views
How to find N most populous cities in each state with TakeLargest and Entity Functions without waiting forever using Caching?
I am interested in using Entity Functions such as EntityValue, FilteredEntityClass, EntityFunction, EntityClass, EntityList, and GeoEntities to help me find N most populous cities in each state. I ...
- 1,653
0
votes
1
answer
63
views
Mapping data from 2 files imported
I'm not in prog major. This course is needed as an elective for another major. Thus any help is appreciated.
DataA and DataB ...
- 1