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.
1
vote
2answers
395 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 ...
-4
votes
2answers
148 views
How to correctly call a Module within another Module?
How to embed and call the correct embedded modules inside another Module?
Say:
...
-1
votes
1answer
170 views
Multivariate Function Approximation With a Large Dataset
I have a nice amount of data from a trading strategy I am working on, where I have two different liquidity parameters as x, y variables.
Before entering a trade I am taking the moving average of ...
12
votes
2answers
181 views
Pattern that matches colors
Suppose I'm writing a function that takes a color as a parameter; for example:
drawShape[color_] := Graphics[{Style[Disk[], color]}];
But if the caller inputs an ...
5
votes
2answers
126 views
How is OptionsPattern[] defined? Can I replicate this?
I am writing several functions which all take similar input parameters (a complicated nested list structure). Is there some way for me to define a pattern that can be used in multiple places and ...
1
vote
1answer
111 views
Find the derivatives of arbitrary order of a function found using NDSolve
For the following initial value problem
BC[b_]:=x[0]==b;
eq[b_]:=NDSolve[{equation==0, BC[b]}, x, {t,0,1000}];
body[t_,b_]:= x[t]/.eq[b];
one could define the ...
1
vote
1answer
73 views
Why function is evaluated backward?
I have a simple function:
f[x0_,y0_]:= Module[{x=x0,y=y0},For[i=0,i<2,i++;Print[x],Print[x+y]];]
So when I call it:
...
1
vote
3answers
245 views
Generating pairs of additive and multiplicative factors for integers
Given an integer $n$, I want 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 came up ...
2
votes
0answers
194 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 ...
1
vote
0answers
97 views
Return Functions from parallel execution of module
I wrote a module which numerically solves an ODE using NDSolve. The result from this is e.g. either ...
0
votes
1answer
67 views
Defining functions from expressions of variable lengths
I have a list of symbols that I have defined using
d = Table[Symbol["d" <> ToString[i]], {i, 1, n}]
giving
...
6
votes
2answers
309 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
76 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}}
...
1
vote
1answer
245 views
Matrix Multiplication Modulo 2
I would like to perform matrix multiplication modulo 2. Hence, instead of the usual:
A.B
I did:
...
0
votes
1answer
127 views
0
votes
0answers
88 views
3
votes
4answers
164 views
How to create a composite function from a variable number of components?
Background of the problem: A patient takes a drug every $X$ hours with a half-life of $Y$ hours. How much of the drug will be (exactly) in his system after $h$ hours? For $X=24$, and $Y=24$ I made the ...
2
votes
1answer
112 views
Implementing a For (?) or series or loop (?) for individual results for every x to n
I'm working on improving a modeling formula and have spreadsheets worth of data to use, but my work so far has been quite tedious. I'm essentially pulling 20 rows of data from each separate sheet of a ...
0
votes
3answers
137 views
Better solution than returning a list of 3 values?
I have a function (using SetDelayed) that currently returns 3 values in a list. Later on I use the result of this list along with ...
2
votes
1answer
138 views
Defining a function that handles Dynamic arguments similar to Built-ins
Firstly please note that I'm using simply Dynamic behavior to illustrate my question, I'm not asking how to move a Disk or make ...
2
votes
2answers
86 views
1
vote
2answers
104 views
How to mix Unevaluated property of function arguments with expression assignments?
This is a follow-up to my (solved) question How to distribute a generic function of two arguments (without evaluating the arguments)
Say, I have a binary function
...
4
votes
3answers
110 views
How to distribute a generic function of two arguments (without evaluating the arguments)
I guess there is an easy way to do this, but I can't seem to figure it out. What I would like to do is to distribute a generic (i.e. without specifying what this function really does) binary function. ...
6
votes
3answers
221 views
Composition of mappings not working as expected
I have two functions $f,g:\mathbb{R}^2 \to \mathbb{R}^2$ and I define a third one $h:\mathbb{R}^2 \to \mathbb{R}^2$ as the composition $$h(x,y) = g(f(x,y))$$
I'm trying to get this function into ...
4
votes
2answers
173 views
Define product derivative
How do I define the $n$th product derivative of a function in Mathematica?
The first product derivative $f^\ast$ of a function $f$ is
$$
f^\ast(x)=\exp\left(\frac{f^\prime(x)}{f(x)}\right)
$$
The ...
3
votes
3answers
165 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
75 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 ...
1
vote
1answer
633 views
“Tag times protected” for this doesn't make sense
I have a property calculator which is in a Table to generate well... a table of properties and growth rates depending on the value of ...
4
votes
2answers
142 views
Function to select a row whose kth element is closest to a given number
I'm trying to write a function that picks out the row of a Matrix whose kth element is closest to some given number that will be given to me.
So for example,
...
9
votes
1answer
143 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 ...
9
votes
2answers
262 views
NestList on a function with more arguments
I'd like to know if it is possible to use NestList on a regular function with more arguments, such as:
...
4
votes
2answers
896 views
How to find (numerical) value of a derivative at point?
I have the following function:
f[0, 0] = 0
f[x_, y_] := Exp[-(x^2 + y^2)^(-1)]
How do I find its partial derivatives at any given point, including $(0,0)$? This ...
2
votes
2answers
131 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:
...
9
votes
1answer
305 views
Functional programming and Do loops
I'm writing a Monte Carlo simulation. I'm using a Do loop to create the different simulations, iterating over different ...
12
votes
1answer
143 views
Is it possible to Clear all variables (but not functions)?
I have written a Mathematica script in which I define functions and variables. Here is a vastly simplified example:
...
11
votes
2answers
212 views
can a ColorFunction have side effects?
Can anyone explain this (to me) odd behavior. If I run this code once (fresh kernel) it works as intended.
...
1
vote
2answers
187 views
Using Functions as Arguments to Function
I am trying to make a function like Norm but defined like so: MyNorm[{x_,y_,z_}]=Sqrt[x^2+y^2+z^2]. Mathematica assumes that x, ...
8
votes
2answers
202 views
Generating a position lookup function for an arbitrary list of integers
In my code, I generate a list of integers called numlist. Here is an example numlist:
...
1
vote
2answers
182 views
Piecewise function with a function as argument
I want to define a piecewise function, which has two arguments, one of which is a function of the other's piecewise argument. I am giving an example
...
1
vote
2answers
101 views
How can define a set of nested parameters
I would like to know how I to define a function with a nested set of parameters (or whatever you would like to call it). For example, how would I get the following function ...
1
vote
3answers
157 views
Variables Inside Functions Not Evaluating
x = 5*y
function1[y_] := x
function1[5]
Am I wrong in thinking that function1[5] should equal 25? Instead this comes out.
...
1
vote
1answer
166 views
3
votes
4answers
120 views
Pack Solve results into a vector
I am currently using a really easy function to get the eigenvectors of a corresponding eigenspace:
...
6
votes
3answers
201 views
Where in the documentation can I find a list of function argument types?
Recently, I learned that it is possible to assign "types" to function arguments in the definition of a function. Suppose I have a function stringFun that does some ...
22
votes
6answers
668 views
Convert an expression to a Function
I need a function which can take an expression and return a pure function based on the symbols in the expression. The symbols might have values so must be protected from evaluation. It is probably ...
2
votes
9answers
922 views
How to find palindromic numbers (Project Euler #4)?
I'm trying to solve the fourth Project Euler's problem with this:
...
4
votes
2answers
125 views
Standardizing a coset table via matrix manipulation
Suppose we have a group $G$ and a subgroup $H$. A coset table encodes the permutation representation of $G$ on the right cosets of $H$. When we want to use these coset tables in calculations, it is ...
5
votes
4answers
321 views
Swap two entries in a matrix
Is there a nice, simple script one can use to swap two entires in a matrix? For example, suppose we have the matrix below:
$A=\begin{pmatrix}2 & 4 & 1\\
3 & 1 & 2\\
4 & 3 & 1
...
3
votes
2answers
181 views
Defining a function using Series? [duplicate]
Possible Duplicate:
General::ivar is not a valid variable when plotting - what actually causes this and how to avoid it?
I need to define a function using the output of series, i.e.
...
4
votes
1answer
162 views
Finding mappings between expressions
Suppose we have an expression of the form:
$j=\frac{A\left(t\right)}{B\left(t\right)}=\frac{C\left(s\right)}{D\left(s\right)}$
That is, $j$ can be expressed either as a function of $t$, or as a ...
