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

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7
votes
3answers
229 views

Mapping a function over the parts of a deeply nested Array

I have two tensors: tensorS = Array[Subscript[s, #1, #2, #3, #4] &, {2, 16, 16, 19}]; tensorR = Array[Subscript[r, #1, #2, #3] &, {2, 16, 19}]; ...
6
votes
2answers
159 views

Is there a built-in function to map a list of heads to a list of data?

Assume that this built-in function is called func. What I want is func[{f,g},{a,b,c}] will return the following result: <...
4
votes
4answers
141 views

Plot range of a 2-dimensional function as a function depending on one variable

I want to plot a function of 2 variables x and y, for discrete values of y, like: ...
0
votes
1answer
211 views

Map Elements of a list to be Index of matrix

I have a sublist from Tuples[{1, 2, 3}, 2], say for example L={{1,2},{2,1},{2,2}}, and a 3 x 3 matrix ...
6
votes
2answers
510 views

Apply function to every element of list regardless of depth

I want to apply a function to every element of a list without taking braces into account (depth level), but with the same form of output. Here is an example : ...
0
votes
1answer
129 views

ParallelMap returns incorrect results over Map

I've written a function to pull in the useful column of a large data file: ...
33
votes
3answers
2k views

Changing Values in an Association using Map

I am trying to change the value of one key in an association based on the value of another key in that association. So if my association starts as: ...
2
votes
2answers
159 views

Map 2 list to a function

Im playing around with CountryData and I want to pass it 2 lists as argument, listCountries = {...} and ...
5
votes
1answer
559 views

Why is there a huge performance gap using Map with more than 100 List entries

im using Map on a List like this: cube= {{1, 1, 1}, {1, 1, 2}, {1, 1, 3}, {1, 1, 4}, ... , {5, 5, 4}, {5, 5, 5}} Mapping the whole List with 125 entries takes ...
2
votes
1answer
113 views

Can I use Map here rather than Table?

I've got something that works, but it seems like it would be "nicer" if I didn't have to use Table (or For, etc.). I've got 3 Excel files, each with multiple sheets. Each file also has a sheet ...
3
votes
4answers
171 views

Correct slot assignment when mapping from different lists using pure function

Given expr = u == a1 + a2 x + a3 y; and uRep = {u1, u2, u3}; xyRep = {{x1, y1}, {x2, y2}, {x3, y3}}; I'd like to generate ...
0
votes
1answer
49 views

Testing a certain function over multiple levels

I regularly want to test if a certain function, here foo, gives the expected result when mapping it over n - level - matrices. My naive approach is to write: ...
2
votes
1answer
226 views

Loop in solving multiple matrix calculation

I am wondering is there a way to use loop, like Do, For, to rewrite the last line in the code. I tried to use ...
0
votes
1answer
255 views

Mapping a function over n levels

I want to map a function over a matrix of rank n, for example: ...
0
votes
1answer
107 views

How do you add options to a function that is being mapped?

Simple example: Normally: ListPlot[list, Joined->True] If I want to map ListPlot how do I keep the ...
5
votes
1answer
88 views

MapIndexed stops at levelspec 1 if only the index is passed?

If the function passed to MapIndexed references the first (or data) argument, the following performs as expected: ...
32
votes
2answers
2k views

Scan vs. Map vs. Apply

I cannot understand the difference between Apply, Scan, and Map. I have tried to play with ...
2
votes
1answer
206 views

Country borders and grids with CountryData plot?

I am coloring several countries in the manner of the following: ...
0
votes
2answers
467 views

Apply Eigenvalues to a list of matrices

I would like to apply Eigenvalues[] to a list of matrices as in the following ...
3
votes
2answers
335 views

Mapping multiple functions over an array

I am looking for an elegant way to Map multiple functions over an array. My problem looks something like this: Consider a list of functions: ...
0
votes
0answers
38 views

Using Map with functions that take a parameter [duplicate]

I have a list l={{0, 0, 0, 3}, {0, 0, 0, 3}, {0, 0, 1, 2}} And I would like to obtain the number of zeros in each sublist: ...
3
votes
4answers
396 views

How to apply a function of several arguments to a list?

I have a list of triplets: list = {{1, 3, 5}, {4, 5, 1}, {4, 9, 2}} How can I apply a function f to the last element of each triplet when f the last and second-...
0
votes
0answers
34 views

Use Map with OptionValue [duplicate]

Trying to map OptionValue to a list of option names doesn't work. ...
0
votes
1answer
62 views

Function output of two lists are only diagonal elements

I'm having a little crysis over here. What I basically want to do is some sort of 3D-Plot, but I'm only interested in the resulting values. I have two vectors x and p: ...
4
votes
1answer
150 views

Parallelize[Mapindexed[]], level={-1}? Sal Mangano's 《Cookbook》

It is easy to Parallelize[] Map[] & MapIndexed[], as having been shown in MMA9 Help for ParallelMap[] and Parallelize[]. For MapIndexed[], the default levelspec is {1}. However there are many ...
2
votes
3answers
302 views

Distinguishing slots in a function mapping Position across a list

Suppose that I have a list myList that has more than one level. Here is an example of such a "data structure": ...
1
vote
1answer
348 views

MapThread multiple functions onto multiple lists

I'm trying to learn the functional style which seems to prevail in Mathematica. I'm having trouble accomplishing the following: Let's say I have multiple lists of arbitrary data (using two lists ...
0
votes
1answer
72 views

Mapping a function of two arguments where the 2nd arg has a fixed value

I create three random images: i1 = Image[RandomReal[1, {8, 12, 3}]]; i2 = Image[RandomReal[1, {8, 12, 3}]]; i3 = Image[RandomReal[1, {8, 12, 3}]]; I can scale a ...
2
votes
0answers
104 views

Want explanation of when different looping constructs are appropriate [duplicate]

For example when would you use a Do loop over a For loop? For which tasks would you use Map, ...
1
vote
1answer
130 views

MAP a business cycles model

There is a Business Cycles Map on Phaser 3.0 and I've trying to run it on Mathematica the last four days without succes. The equations are $$ x_1 = (1.0 - a s)x_1 + a \left[s m + g \left(\frac{s m}{...
4
votes
2answers
142 views

Can one use Map during Expand?

Can one Map a simplifying function to the summands of an Expand before fully expanding the expression in question first? ...
10
votes
8answers
628 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 ...
0
votes
2answers
323 views

Using a table to format a grid

Ok, I can't wrap my head around this because I don't know Mathematica well enough yet, so I'm asking for help, at least a direction to explore in. I have a Grid: ...
0
votes
2answers
171 views

Drawing a large set of Graphics3D cylinders provided a set of cylinder specifications in a list

I'd like to draw a large number of 3D cylinders using Graphics3D. My list specifying the cylinders has elements that look like the following: ...
8
votes
3answers
335 views

finding anagrams

What I'm trying to find are the 4 letter words in the mathematica dictionary that have the most anagrams and the amount of anagrams these have each. But I can't seem to find all the 4 letter words in ...
-1
votes
1answer
122 views

map rational number [duplicate]

I am trying to map this function ((-1)^(1/Denominator[#]))^Numerator[#]==(-1)^#& to a fairly big list of random rational numbers I am trying to get this to ...
4
votes
1answer
288 views

MapThread Alternatives

I want to add two matrices, the first one containing a 2D vector at each position the other one a list of 2D vectors. The 2D vector from the first matrix should be added to each of the 2D vectors at ...
4
votes
1answer
196 views

MapThread and Compile

After discovering that MapIndexed cannot be used with compile (see MapIndexed and Compile) I am now trying do implement similar functionality using a combination of ...
0
votes
1answer
119 views

Problem with List Dimension Outer Map [duplicate]

I am currently handling a big list which has the following dimension: {6, 3, 4, 2, 2, 1, 8} where the last number 8 represent a ...
2
votes
1answer
125 views

Can Map operations be compiled or otherwise sped up for large lists?

I'm performing a series of Map operations in the following script: ...
1
vote
2answers
262 views

How to apply function f for each time value t, to each pixel from image, resulting in t images

I have a 2D array of complex values and I want to apply a function to every entry of the array, for every timepoint t in a list. I know how to apply my function to one entry for every time t in a list,...
1
vote
1answer
257 views

Map a function conditional on elements at multiple relative positions in a list

I figure this question has many solutions, and if an answer already exists it would be nice just to be referred to it. I need a function that 'maps' over my list and produces a list of equal length ...
4
votes
1answer
595 views

Using Thread or MapThread over multi-level, ragged lists [duplicate]

This may be a rather strange question. I will try to create a sort of minimal working example. Suppose that I have two lists, list1 and ...
11
votes
6answers
390 views

Using MapIndexed only at certain elements of a list

MapIndexed is a very handy built-in function. Suppose that I have the following list, called list: ...
10
votes
5answers
626 views

Span a function across several consecutive elements in a list

Suppose that I have a list called list. I would like to span an arbitrary function f across specified consecutive elements in <...
10
votes
3answers
3k views

Mapping a pure function with multiple slots [duplicate]

Here is a pure function with multiple slots: (#1^2 + #2^2)&[3, 4] 25 But how can I map that pure function over lists of values? For example, say I want ...
8
votes
2answers
459 views

Using Map with If

I have an If statement I need to carry out where the result should be a single number for each time the if is executed. What I have at the moment returns a list for each time the If is executed. I ...
3
votes
3answers
169 views

Applying a function of several arguments to the rows of a matrix

I have a user-defined function which takes three vectors as input. Suppose that is like this: f[a_, b_, u_] := Total[a*Total[u]^b] Usually I have vectors for <...
6
votes
2answers
264 views

Variable scoping problem when mapping over delayed replacement

This is something that got me curious while I was playing around with Mathematica. Consider the following (contrived) example: ...
5
votes
1answer
172 views

How can I substitute something using only map?

For example, I have the equation x^2 + y^2 == x*y and I want to apply the rule y -> s*x I can do it easily by ...