Questions tagged [map]
Questions about applying functions or operators to expressions, especially constructs that take advantage of Map (/@) functionality.
274
questions
1
vote
0answers
64 views
Is there a good reason why `Slot[]` is not an atomic expression?
Here's a good reason why I think it should be,
Map[ If[AtomQ@#, #->"is an atom", #->"not an atom"]&
, {"hello",Range@3, # &}
, {-1}
]
...
8
votes
3answers
415 views
Map a function that takes arguments in different levels of a list
I would like to map a function that takes as an argument a list in a list of lists and an element of the list of lists.
So for example, this is my list of lists:
{{4,1}, {3,1,1}, {2,2,1}}
I ...
1
vote
1answer
38 views
How can I consolidate mapping code between different levels of lists?
I have a list with the following structure:
...
5
votes
4answers
410 views
2
votes
2answers
90 views
Map vs. Table for index-specific operations on 2D arrays–Part II
This is an extension of my recent question, Map vs. Table for index-specific operations on 2D arrays
For that question I gave a minimal working example, since I was more interested in learning ...
1
vote
1answer
42 views
Combine a List of Plots: Using MapThread with Show [closed]
I have a list of graphics
p1 = Plot[x Sin[x] - 1, {x, -2.5, 2.5}]
p2 = Plot[Evaluate[D[x Sin[x] - 1, x]], {x, -2.5, 2.5},PlotStyle -> Red]
ListNew = {p1, p2};
...
2
votes
3answers
108 views
Map function over two lists
How to map a function over two lists, first one and than the other?
For example, assuming I have two lists {a,b,c} and {d,e,f}:
...
13
votes
2answers
354 views
Map vs. Table for index-specific operations on 2D arrays
Many experienced users on this site tend to use Map (and its variants, MapAt, MapIndexed, etc.) rather than Table. When applying the same operation to every element of an array, Map does seem more ...
7
votes
2answers
92 views
Creating a new Dataset column using a map from a second Dataset
Say I have two datasets: one is a detailed list of events, and one is a coarse list of events. I want to add a column to the detailed list from the coarse list (for the purposes of sorting).
For ...
0
votes
0answers
63 views
A map function in a simulation problem
This is a continuation development of another post by @Dr. Wolfgang Hintze and deserves credit for the code work presented here. My modification was to include simple mapping to allow compare the ...
1
vote
1answer
44 views
Moving map with non-overlapping window
How can I apply a function to a list with non-overlapping window. E.g. $data = \{x_1, x_2, ...., x_n\}$ and we apply f with window size 2 to get $\{f(x_1,x_2), f(x_3, x_4), ...., f(x_{n-1}. x_n)\}$.
...
3
votes
2answers
194 views
How to find the positions of replaced elements in a list
I have two sets of elements
a={3, 4.8, 5, 4.2, 3.6, 2.3, 4.5, 3.7}
b={2.8, 4.7, 5.3, 3.5, 4.7, 2.8, 4.2, 3.4}
and I create ...
6
votes
8answers
2k views
Simplify the code
I have a function that grabs the second part of the list and change it to times,
...
4
votes
2answers
161 views
Iterate MapThread with matrices
Consider a function f and a list p={a,b,c}. I want to get a list of
...
1
vote
1answer
35 views
Summing up elements of nested lists based on conditions from another list
Here is a simplified version of my question, nothing that I have a much larger dataset.
I have a list of samples of proportions:
...
4
votes
2answers
192 views
List of lists elementwise greater/smaller than
I have two lists
a = {{3,1,2},{5,1,3},{4,1,1}}
b = {{4,0,3},{4,2,2},{5,0,2}}
And would like to compare each element within
...
1
vote
3answers
63 views
Mapping a function with levelspec vs. Mapping over a flattened list
I have borrowed the following cyclic permutations list making function from here.
...
0
votes
1answer
82 views
Arrays, Mapping, and Convolutions
I'm trying to create a function that convolutes a 3D Normal Distribution to the points listed below. However, I think I'm going about it in the wrong way.
When I try and convolve it with the points, ...
1
vote
1answer
53 views
Replace second derivative with product rule
Suppose that after some calculations, I find
a[x]*D[g[x],x,x]+b[x]*D[h[x],x,x]+c[x]*D[j[x],x]
What sort of operations do I need to do in Mathematica such that ...
1
vote
1answer
30 views
Mapping the FindMinimum function over a matrix
I'm quite new to Mathematica and so still trying to work out how to use some of its syntax and functions. I have a function for the free energy of a generic system with two order parameters. I am then ...
0
votes
1answer
29 views
1
vote
2answers
76 views
How can I iterate across a list of triples?
i just started to use Mathematica and I`m completely new to programming. So i'm some kind of noob in the purest form..
I'm trying to transform a coordinate system into a different one. I'm using <...
6
votes
1answer
72 views
How to properly Abort from within a ParallelMap?
If a condition is met within a sub-kernel in the function being mapped, how does one cancel the whole ParallelMap operation?
...
0
votes
1answer
52 views
Using elements of list to solve a differential equation
I have created a list as shown in picture.
the digits inside f are values of a and q respectively.
I want to solve the Mathieu equation.....
2
votes
0answers
38 views
Map a function at the lowest level [closed]
How do I map a function to the lowest level of any given nested list? As an example, how do I create output from input in the ...
2
votes
1answer
81 views
Fast and Listable Piecewise function
I am writing a simulation where I have an array with ten columns and on the order of millions of rows, for which I need to iterate on the order of ten thousand times, making computation time a major ...
0
votes
0answers
30 views
Help with weird behaviour of Map[Take… on large lists
Lets say I create a giant list:
tmp=RandomReal[{1,10},600000000];
Now I want to take 10 random sublists of length 150000:
...
4
votes
1answer
142 views
Apply Max to each element of a list [duplicate]
I have a list
a = {1, 8, 0, 6, 5, 3, 5, 2, 2, 5}
I want to generate a new list whose elements are the same of a if it's bigger than 5, or 5 elsewhere.
I managed ...
2
votes
1answer
123 views
How to compute Maximum Drawdown faster and highlight data-list-line on the plot?
Given a list as
...
1
vote
2answers
77 views
How to caculate Position Cost Price in given trading list quickly?
Given a simulated trading list as
...
0
votes
1answer
23 views
Table of convolutes
Inputs
Start with a vector $x\in\mathbb{R}^{n}$, and a vector-valued function $f:\mathbb{R}^{n}\mapsto\mathbb{R}^{n}$.
Output
Given some $k\in\mathbb{Z}^{+}$, what are elegant ways to produce the ...
10
votes
1answer
102 views
Parallelize[MapIndexed[…,Association[…]]] returns broken result
Bug introduced in 10.0.2 or earlier and persisting through 12.0
Confirmed: CASE:4041910
Consider the following example:
...
1
vote
1answer
51 views
Mapping over a piecewise function
This is a followup to a question I posted earlier today. Suppose you have a piecewise function such as "snap=max[x,0]= x if x>0, 0 otherwise".
Then you would think that it must be straightworward to ...
0
votes
0answers
52 views
Using Map function with NDSolve
I would like to solve a set of differential equations but vary one parameter, KieP, between 900 and 1100.
The solution for a given parameter has many peaks. I would then like to interpolate between ...
0
votes
1answer
53 views
How to map a function to a specfic level spec
I'm rewriting a function into a manipulatable graphic and while I'm happily surprised with how concise functional programming can be, I'm having trouble mapping the anonymous function ...
13
votes
2answers
480 views
Project map to a particular shape
I want to project a map to a particular shape, like a circle or ellipse. For example, let's imagine we want to project a map of the continental United states so that its outline is that of a circle. ...
0
votes
0answers
99 views
Operation on sublists with multiple arguments
I have a list and add only the values which are > 0 with:
Total[Cases[mylist, x_ /; x > 0]]
How to do this if I now have a list of sublists?
...
1
vote
0answers
72 views
Run function as loop over two matrices
I'm still wrapping my head around Mathematica syntax. I have a matrix clustersAll that looks like
...
1
vote
0answers
84 views
0
votes
0answers
88 views
How to give a function multiple variables in a mapped and nested list?
I come from python (not advanced tho), and have been learning mathematica. I'm currently struggling with the following code:
This is a basic version of what i wanted to implement:
...
3
votes
4answers
171 views
@ and Sequence ( and /@ ) [duplicate]
list = { {a,b}, {c,d}, {e,g} }
How to efficiently get
{ f[a,b], f[c,d], f[e,g] }
I tried various combinations using ...
2
votes
2answers
150 views
Clear variables inside Module
I have a function that uses Module. The function takes as input a .csv that can have as many columns as it wishes to, and it ...
3
votes
1answer
53 views
Can I Use a List To Position An Arbitrary Number of Graphic Objects?
I can use a function to compute the positions of individual nodes of a neural network based on how many there are in each layer (nodesPerLayerList below). Now I want to display them all in position. ...
6
votes
2answers
259 views
Applying functions to lists
I have a few expressions $f(\theta,x)$, $g(\theta,x)$, $h(\theta,x)$ in terms of two variables, an angle and a length. The angle goes from $-\pi/2$ to $\pi/2$ and the length from 200 to 1500. This is ...
0
votes
2answers
120 views
Mapping slots over lists
In the meantime I'm accustomed to write special character orgies like D[%,#]&/@L (to quickly fish out the coefficients of the last input with respect to ...
1
vote
0answers
29 views
Color filling by GDP in a map
I would like to have a tool where one can type in a minimum GDP level and then every country that has this minimum level gets filled with color.
1
vote
2answers
75 views
How to I use Map to apply a defined function to a list?
Problem: How to map a function onto a list.
My (example input:
mylist = {{1, 2}, {3, 4}}
gg[x_, y_] := {N[x + y], N[x y]}
Map[gg, mylist]
Expected output:
...
1
vote
1answer
62 views
Angle between one vector and a list of vectors [closed]
I have one vector v1 and one list of vectors v2. I want to find the angle between them (see below):
...
8
votes
1answer
125 views
How to Parallelize a simple MapAt?
I have a simple map I would like to parallelize (4x speedup for my 4 cores):
...
2
votes
1answer
77 views
Extracting the graph of Keys in nested Associations
Related to this q: Extract all Values from nested Association
How to extract the direct graph of all Keys in nested Associations...
