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

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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 ...
5
votes
5answers
501 views

another way to do this mapping of a two argument function

Sorry, I'm just starting to learn mathematica. I have the following two-argument function: h[{x_, y_}] := x ^ y When I do the following: ...
7
votes
1answer
775 views

nested use of Apply/Map/MapThread in pure functions

1. My main question I have a function with two argument slots. I wan't to apply this function to 2 lists with different length's. I thought in this solution: ...
1
vote
2answers
87 views

How to construct a new list made from a function that operates on two lists

I need to take two lists (each list contains the number of moles of a chemical). I have a function calledFraction that takes the each entry of the list and then calculates the mole fraction of ...
1
vote
3answers
167 views

Placeholders for map inside a map

I have a list structured like list1 = {{"header1","header2","header3"}, {0,1,2}}; and I'm using a custom function to find the number of the column with a ...
3
votes
3answers
211 views

Dynamic application of several polynomials

I know how to get the 'resulting image' (y) from the application of a certain function (f) (here represented as the coefficients of a polynomial) over a certain interval (x): ...
3
votes
1answer
238 views

Issue with ListConvolve

I am a new Mathematica user, learning the intricacies of functional programming. I have issues withe applying a function over a moving list. My function seems to work and give correct results but it ...
2
votes
2answers
227 views

Using DeleteCases and Map together

Given: list1 = {{"a",1},{"b",2},{"c",3}} I would like to delete any pair in list1 that does not have a first element that belongs to list2. Example 1: If ...
3
votes
3answers
654 views

Efficiently compute double sum

Is there a "Mathematica Way", like Map or Apply to compute the following double sum? $\sum_{i=1}^{N_1}\sum_{j=1}^{N_2} m_i n_j \, f(\tau_{i} \gamma_{j})$ I have already stored the lists $m,n,\tau,\...
7
votes
2answers
1k views

Nested Map and Apply

There are some other questions on this topic but I could not get an answer from reading them. What I want to do is use Apply on some of the arguments of a function, ...
7
votes
2answers
631 views

Map a function over the columns of an M x N array

I have a $N \times M$ list of lists, or rather, a list of records and I want to map a function over its columns (e.g. find the mean temperature, age, etc.). Map ...
11
votes
4answers
410 views

What's fastest way of defining 10^5 down values?

I want to define isGood[___] = False; isGood[#] = True & /@ list where list is a list of several million integers. ...
7
votes
3answers
7k views

Map w/ multiple arguments [duplicate]

Possible Duplicate: How do I use Map for a function with two arguments? If I have a function: F[x_,y_,z_]:=x*y*z and I want to call it with several ...
34
votes
12answers
2k views

Map a function across a list conditionally

It seems that this is a really basic question, and I feel that the answer should be obvious to me. However, I am not seeing. Can you please help me? Thanks. Suppose I have a list of data ...
10
votes
3answers
933 views

how to efficiently apply function to all pairs of a set (and collect the results)

To build a graph, I need to apply a function f[a_, b_] to all pairs of a list (3500 elements). The function itself returns a link ...
1
vote
2answers
208 views

Expectation over a list with nested-mapped expressions

I need expected values of a list where the random variable to take expectations over should be an input into expressions defined earlier. I suspect Set[] and SetDelayed[] tripped me. (Or Map and Table?...