0
votes
0answers
37 views

A problem with functions and Infinite expression 1/0 encountering

Following code (function) makes integrals and then replace f[x] with Cos functions and calculate the definite parametric ...
0
votes
1answer
74 views

A problem with set values

The following code is just an example to clearly explain my problem. Assume that : ...
1
vote
1answer
66 views

Need help defining my own rounding function

First of all: I'm a beginner with Mathematica. I'd like to define a function called Rounding which does the following: if for $x = n+a, n \in \mathbb{N}, a\in ...
1
vote
1answer
100 views

How to replace a list with the result list after each iteration [closed]

I have some initial values such as L1 list: L1={10,20,30,40,50}; I want to use the L1 ...
3
votes
1answer
153 views

Extracting function calls from an expression

I have an expression like this: expr = F[0, 1] + 2 F[0, 0] - 17*F[2, 0] and I want to transform it to a list consisting of all function calls with its arguments: ...
1
vote
2answers
133 views
12
votes
4answers
337 views

Equivalent Nested Loop Structure

Consider the following examples: ...
6
votes
3answers
140 views

Using PatternTest and/or Condition to detect equal list lengths as well as list element formats

On searching Mathematica.SE for information about overloading functions, I came across several threads about PatternTest and ...
5
votes
1answer
166 views

How can I define a Listable function only apply to a vector?

Consider the function f which should behave as f[{{1, 2}, {3, 4}, {5, 6, 7}}] ...
16
votes
12answers
1k views

Pick elements of largest absolute value

For example, given list = {{1, -3, -5}, {2, 1, 6}, {0, 2, 4}, {-9, 2, 6}} should return: {-5, 6, 4, -9} Updated I found ...
6
votes
3answers
832 views

Simulate MATLAB's meshgrid function

Here is MATLAB's meshgrid. I came up with these implementations in Mathematica: ...
2
votes
1answer
80 views

Map and Scan ignore HoldFirst

I am trying to write a simple function that takes a list of data and outputs it to a file. I'd like the name of the file to be the same as the variable that holds the list. It seems that giving a ...
14
votes
7answers
564 views

A function that accepts a pair or a list of pairs

Probably a duplicate, but it's not easy to search on "lists". I have a function that accepts a list of lists, say {{a1, b1}, {a2, b2}, {a3, b3}} and performs some ...
5
votes
3answers
196 views

Applying a function with the HoldAll attribute inside NestList

I'm trying to write an update function, which can be applied to a list and then to NestList it. As the function has to manipulate the given variable I figured I ...
5
votes
4answers
366 views

Any rule of thumb for converting a simple mathematical expression into a pure function?

By simple mathematical expression I mean one with a few functions and few variables copied into MMA in a mechanical way from a math book. For example this one, giving the distance between two points ...
19
votes
1answer
358 views

How can I make threading more flexible?

Threading automatically with Listable functions requires the argument expressions to have the same length (or for one of them to be atomic). For nested lists the ...
9
votes
4answers
244 views

How to pass a list of arguments into HoldAll

I have a list of arguments (which in reality is lengthy): arguments = {a, b, c} arguments2 = {a_, b_, c_} f[Sequence@@arguments2] := a + b + c Note: It seems ...
4
votes
2answers
147 views

How to only work on sublists with non-zero (or positive) values

i have a large compositional dataset which contains non-zero and zero values. here is a sample: ...
11
votes
3answers
850 views

What is Mathematica's equivalent to MATLAB's filter function?

The MATLAB code filter(0.5,[1, -0.5], [1:10]) is equivalent to Rest@FoldList[(#1 + #2)/2. &, 0, Range[10]] I don't ...
1
vote
1answer
123 views

Creating an array eval [closed]

How can I create an one dimensional array (a vector) evaluating a function of two variables? I know how to do it with one variable: Array[f, n, {a, b}] generates a ...
1
vote
1answer
92 views

How do I define a function that, when given a list of parameters, plots a family of functions?

So far I've got this: draw[a_, b_] := Plot[{f[a, b[[1]], x], f[a, b[[2]], x]}, {x, 0, 5}] The function draw will be used like ...
4
votes
6answers
197 views

Filter list with different list in it

I have a list like: {{{4, 14}, 1}, {{4, 15}, 1}, {{4, 16}, 1}, {{4, 17}, 1}, {{4, 18}, 1}, {{4, 14}, 3}, {4,15}, {{4, 16}, 2},{4,18}} Now I want to ...
2
votes
3answers
366 views

Generating pairs of additive and multiplicative factors for integers

Given an integer $n$, I want to get two lists: a) the set of pairs of the divsors $a,b$ into exactly two factors $n=a\cdot b$, b) the set of pairs $a,b$ of two summands $n=a+b$. The code I ...
2
votes
0answers
289 views

Generating a function which outputs possible chemical reactions

I want to make a list of chemical reactions and I write them down in a $\require{mhchem}\LaTeX$ format. They are of the following form $$NA_n^i+MB_m^j \rightarrow \hat NA_{\hat n}^{\hat i}+\hat ...
7
votes
2answers
1k views

Building matrices by attaching vectors (columns) and matrices

Having the need to attach a column to a matrix or to join matrices to make longer rows is an operation that I use very frequently and I find the Join function ideal ...
1
vote
0answers
84 views

Non Commutative Multiply [duplicate]

Possible Duplicate: Non-commutative symbolic linear algebra I want to multiply two matrices, for example, A = {{e, f}, {g, h}} B = {{a, b}, {c, d}} ...
3
votes
3answers
274 views

How to pull scalars out of a function that should act on lists?

Suppose I have A = a vecA B = b vecB where a and b are supposed to be arbitrary scalars ...
2
votes
1answer
108 views

Specifying form in MemberQ

This seems like a very simple question, the answer to which should be obvious to me. So I won't be offended if this question is closed. But I'm having trouble figuring out the answer. I would ...
2
votes
2answers
142 views

Constraining a random function

This question is a follow-up from here. I have a function that generates a list of correlations between some random variables: ...
3
votes
3answers
142 views

Function[] argument nesting for operations like Select[]

The following code selects a special element from a list thelist = {"this", "notthis"}; Select[thelist, (# == "this") &] What I want is a function which ...
16
votes
3answers
617 views

Using pure functions in Table

I need a table with the elements made of pure functions and list elements. This is a simplified example: I need a list as: ...
35
votes
3answers
960 views

Tiling a square

I wondered if there was a way to automate the process of finding a way to tile a tile into a square. The idea is to represent the tile with a matrix of $0$s for blank space and $1$s for filled spaces ...
16
votes
9answers
845 views

How do you check if there are any equal arguments(even sublist) in a list?

I would like to set up a function which has to return True if at least two arguments of a given List are equal. So if I give {1,4,6,2} to the function it has to ...
25
votes
4answers
513 views

How to make MapAt work with Span?

Span (;;) is very useful, but doesn't work with a lot of functions. Given the following input ...
14
votes
5answers
735 views

Picking random items out of a list only once

I'm trying to create a function that randomly returns a value from a list but remembers the values that have been given before. At the end when the list is empty it should return an empty list. ...
4
votes
1answer
216 views
4
votes
1answer
190 views

What's the most intelligent way to store the information of a selfmade graph?

I have a very long list of element, say $a1,a2, a3$,..., and they are all connected in that each is the child of many parents. E.g. $a74$ is associated with $a2,a55,a71$, and also contains ...