For questions on writing functions (pure or using Set/SetDelayed) for any purpose, including the features that may be incorporated in those functions, such as options, patterns and conditions.
0
votes
0answers
31 views
Nested For Loops that result in no output [duplicate]
I am sure that this is not the most elegant code you will have seen, but I am trying to loop through an expression to see if FultonHarrisn] produces any outputs ...
7
votes
1answer
77 views
Is it possible to use the global definition of a symbol as part of its new local definition set in a Block?
Consider the following expression:
Block[{Print = CopyToClipboard}, doSomething[]]
Now all calls to Print from ...
3
votes
0answers
28 views
6
votes
1answer
104 views
Pattern definition for replacing plus and subtract
Suppose I have two functions $h_1(x)$ and $h_2(x)$, for which we know their sum and their difference:
$$
h_1(x)+h_2(x) = d(x) \qquad h_1(x)-h_2(x) = i f(x)
$$
I have a complicated expression, in ...
28
votes
2answers
506 views
Variable naming changes everything
I am having a rather unusual problem I do not understand with Mathematica where renaming one of the variables of my function causes the function to stop "working". Here is the example of the code ...
1
vote
0answers
60 views
How can I compile function with Apply?
For example, I tried to compile this function but Mathematica gives "The only function arguments supported are Times, Plus, or List", I have no a way to compile this.
...
0
votes
1answer
32 views
Function that displays set of integers fulfilling constrictions
I would like to make a function of three parameters $i$, $j$ and $k$ that displays a list of integers fulfilling some criteria. Specifically the set of integers is:
$\zeta_{ijk} = ...
7
votes
1answer
93 views
FullDefinition and Module local variable
I have a question about FullDefinition and how it interacts with the local variables of Module.
I've created a few functions ...
14
votes
7answers
465 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 ...
12
votes
2answers
187 views
f[arg1, arg2,…,argN] vs. f[{arg1, arg2,…,argN}]
I am trying to reproduce the API of a function (written in R) that accepts an arbitrary number of arguments and handles it the same way as it would handle a single argument that is a list of different ...
0
votes
1answer
55 views
3
votes
2answers
228 views
Why does the first derivative of a piecewise continuous function have discontinuities?
I have this piecewise continuous function which is also continuously differentiable over time :
...
2
votes
0answers
66 views
correct usage of ParallelTable
I am trying to parallelize my script. Here is a MWE of how I have done it:
...
5
votes
0answers
64 views
Is there a function to generate a minimal clique cover?
This is a graph problem known as the "Clique Edge Cover" or "Intersection Number" problem, and the goal is to find, from a given graph like $E=\{\{a,b\},\{a,c\},\{b,c\},\{b,d\},\{c,d\}\}$ and ...
2
votes
3answers
269 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
1answer
98 views
Evaluating a function on permutations of its arguments
Say I have a function "temp" of $n+1$ variables, $y,z1,z2,z3,...,zn$. I want to test if my function has certain symmetries like swapping $y$ with square of any $z$, swapping any two of the zs, ...
7
votes
2answers
92 views
Change some option of a function when calling it
Say I have defined some function like
f[p_] := Plot[Sin[p*x], {x, 0, 2 Pi}]
Now in most cases, I just need to specify the value of ...
-1
votes
1answer
88 views
How to define a pure function with a Module?
I was not able to use a self defined (using Module and For loops) piecewise function to fit data. It seems that the problem is that I have to define a pure function. I would like to learn how to ...
8
votes
2answers
103 views
Possible to scope an anonymous function within Module?
This is my first question. I'm fairly new to Mathematica and completely new to SE, so I apologize if this question is trivial.
I'm working on a problem that requires a function to be redefined ...
1
vote
0answers
42 views
Using anonymous functions instead of module or block. Bad idea? [duplicate]
Here is an example function which returns True if a point p is on an (open) line segment (A, B) assuming that Orientation[A, p, B] returns 0 if the three points are collinear:
...
3
votes
2answers
60 views
How to apply multiple/complicated requirements for a pattern in a function input [duplicate]
In this question. I suggested that to test whether the input of a function was a matrix of numbers one could create the following test:
...
21
votes
4answers
512 views
Why is there no PositionFunction in Mathematica?
Too often I have seen the programs of inexperienced users greatly slowed by using Position in an iterative fashion, when far faster would have been to compute a ...
0
votes
1answer
34 views
Have the kernel load a user-defined function by default [duplicate]
I wrote a very simple function that I would like to act as if it were one of the default functions that came with Mathematica, so that you don't have to load or import any package before you make use ...
0
votes
0answers
49 views
Question regarding function definition overloading / argument passing test [duplicate]
It is possible to define function dependently to passed argument type or condition this argument fulfills (somewhat like overloading):
...
1
vote
0answers
40 views
Unexpected error message from GraphPlot evaluation [closed]
(Running MMA 9 on Mac OSX 10.8.3, MacBook Pro, 16GB RAM)
I am trying to display a graph with GraphPlot. I want a few of the edges to be purple, and the rest red. I figured out a way to do this that I ...
0
votes
0answers
12 views
How to assign values to a function at discrete points? [duplicate]
Suppose we are interested in a function f[x] that is defined only at discrete points:
x = {1.1, 2.1, 3.1, 4.1, 5.1}
We want to ...
5
votes
3answers
123 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 ...
10
votes
1answer
159 views
Modules that initialize themselves on first call
I use a lot of functions that extract a specific data item from a file with many data items. I want these functions to load data (slow) and return the item (fast) on first call, but just return the ...
1
vote
2answers
159 views
Write a function that returns the logarithmic derivative
How can we write a function that if we input an expression f, it returns the log derivative $\frac{1}{f} \frac{df}{dx}$. We have to use a conditional or pattern test so that the function accepts any ...
11
votes
2answers
246 views
Using several anonymous functions mixed together
This works:
list // BarChart[#[[2]], ChartLabels -> DateString @@@ #[[1]], ChartStyle -> "Pastel"] &
This doesn't:
...
3
votes
2answers
95 views
How to define a polynomial/function from an array of coefficients?
I have the coefficients of my desired polynomial in an array CoefArr (I'm new to mathematica, so I think of everything as arrays, it is actually a list I believe) starting with the constant at index ...
2
votes
2answers
74 views
Putting a matrix inside function
I want to fit a function to some data and inside the function there's a list
here's my data
...
-1
votes
2answers
96 views
How can I define a function which is the sum of other functions?
I have a function which is summation of another function over different i,j iterators.
U[r] = Sum[V[r, i, j], {i, 1, 5}, {j, 6, 10}]
and ...
4
votes
3answers
133 views
How can I combine two Pick expressions into one?
I want to speed up my code, i.e., replace Select by Pick. I think using two Pick ...
1
vote
2answers
485 views
How to define a differential operator?
I have a linear differential operator, for instance, $L\left (\partial _{t} \right )=\partial _{tt} - 3\partial _{t} + 2$. I use it in 2 different ways:
apply the operator to a function: $L\left ...
1
vote
1answer
107 views
Mathematica plots a discontinuity in piecewise function that does not exist [duplicate]
I have the following function defined:
...
2
votes
3answers
106 views
Map several functions in one routine
I have several functions, let's assume they are:
func1[x_]=x;
func2[x_]=3*x-5;
func3[x_]=0.1*x^2;
and a lot more like these.
For each and every one of these I ...
7
votes
4answers
291 views
How can I shorten this code to rotate a line segment around its center?
I have a list of line segments stored in the form:
{ {{x11,y11},{x12,y12}} , {{x21,y21},{x22,y22}} , ... , {{xn1,yn1},{xn2,yn2}} }
Now I want to rotate all of ...
5
votes
4answers
251 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 ...
0
votes
1answer
77 views
Strange function definition result [duplicate]
I'm relatively new to Mathematica, and I'm trying to define a function f(k) that would do the following:
For any positive integer $k$, a finite sequence $a_i$ of fractions $\frac{x_i}{y_i}$ is ...
0
votes
2answers
168 views
Why function cannot be defined inside For loop? [closed]
I have a following code (which is simplified version of what I am doing):
For[i = 1, i <= 5, i++,
f[x_] := Sin[x]^2
Print[{i, f[i]}]
]
And the question ...
0
votes
0answers
64 views
How can I get tabular output for the results of my simulation? [closed]
I have code that simulates a simple Markov Chain and looks like this:
...
0
votes
2answers
147 views
Fast Autocorrelation Computation
I want to compute the Autocorrelation Function (ACF) of a data table with $10^6$ entries. I know that there is a built-in function in Mathematica for that, but because I do not know how exactly it is ...
0
votes
1answer
65 views
Function giving negative value when it should be positive [closed]
I am trying to evaluate
$$\displaystyle J=A\sum_{k=0}^{n-2}(-1)^k{n-2 \choose k}B^{n-2-k}\left(\frac{C_1}{k+n}-\frac{C_2}{k+n+1}+\frac{C_3}{k+n+2}-\frac{2}{k+n+3}\right)$$
in Mathematica as a function ...
2
votes
2answers
70 views
Rising Recursion Relationships
Lets say I want to compute the following function in mathematica:
$G[n,k]=G[n+1,k-1] + G[n+2,k-2]$ where I know that $G[n,0]=n$ and $G[n,1]=n^2$.
So, for example, $G[3,2]=G[4,1]+G[5,0]=4^2+5$ or, ...
9
votes
3answers
139 views
Pass by reference for an option argument
Pass by reference can be faked by using HoldAll or something similar in the definition of a "Function". But can pass by reference be faked for symbols passed as ...
3
votes
1answer
195 views
Stereographic Projection
Say I want to represent points of the complex plane in the sphere $\Bbb S^2$ using stereographic projection. That is, the Riemann sphere:
Specifically, it would be nice to be able to:
Given the ...
6
votes
3answers
210 views
13
votes
1answer
135 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 ...
23
votes
1answer
288 views
which is better, using Assert[] or manual checks on arguments and other computations?
I never used Asserts in Mathematica, but trying to see what advantage they have over just argument check and additional definitions of the function to capture unwanted input.
For example, which one ...
