Tagged Questions

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.

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6
votes
1answer
103 views

A question about two ways to use Default

Usually we define a function with default values by the syntax x_:default, but there is another technique to do this by registering a global default value with ...
2
votes
3answers
290 views

Constraining function found by NDSolve to stay positive

I am trying to constrain my variables in NDSolve so that they stay positive for the integration interval. Is is possible to do that? Using Assumptions as in ...
1
vote
1answer
93 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 ...
4
votes
3answers
294 views

Problems using hand-made transformation functions

I experience difficulties when using custom transformation rules. Below I give two concrete problems. I am interested in fixing each of them and in understanding what is wrong with my attitude to the ...
2
votes
2answers
203 views

Defining a function that returns “undefined” if its value is outside of a specific range

I want to define a function f(x) which: $f(x)=x^3 +10x+ 5$ if $f(x) >0$ $f(x)=Undefined$ if $f(x) <0$ I have a idea: ...
1
vote
1answer
118 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 ...
0
votes
1answer
90 views

Multiple Simulations of a Markov Chain

I am trying to create a simple series of Bernoulli bits whose probabilities follow a two-state Markov chain. ...
1
vote
1answer
89 views

How to input pure function to package?

I would like to input a pure function into a custom written package, but am running into a variety of errors. The package I have created is as follows: ...
0
votes
1answer
50 views

How to put some values from a list into a function in a Do loop

I want to program a code in MATHEMATICA in order to calculate some values in different iteration. For example, assume this list: list={1,2,3,4,5} Now assume that ...
1
vote
1answer
123 views
1
vote
1answer
109 views

Requesting explanation of FitModel code

I am struggling with understanding the code given in this original post I understand how the tests are conducted, both of them. However, I do not understand this part: ...
0
votes
3answers
145 views

Clean-up Code / Reduce variables

I'm writing a playing card simulator of sorts, and everything works fine, but some Modules use a disgusting amount of variables. For Example: ...
0
votes
1answer
86 views

Normalize equation in NDSolve?

I have numerically solved and plotted the solution to the Mathieu equation using NDSolve successfully, as below: ...
0
votes
1answer
134 views

Numerical Methods - minimum of a function

Problem: The length of the longest ladder that can negotiate the corner depicted in Figure 2 can be determined by computing the value of theta that minimizes the following function: ...
1
vote
0answers
58 views

Function behavior based on Head

I'm figuring how to implement a function behavior based on the Head of its argument. I mean ...
1
vote
2answers
107 views

Functions of two arguments

I am pretty weak on the notion of pure functions, etc. I found a clean solution to my problem so in a sense I've already answered my own question but I don't feel I'm on terra firma. I wanted to take ...
5
votes
4answers
1k views

“do … while” loop equivalent in Mathematica [closed]

Have I missed something or is there no built-in which mimics the behaviour of do ... while loop? I am looking for a construct that evaluates procedure once and ...
3
votes
3answers
336 views

Alternatives pattern in a function definition

I thought that I remembered a way to write a function definition using "|", but can't find documentation for it. So for example, I'd want to define: ...
0
votes
1answer
87 views

Working with functions

I am required to write a function that takes a function as a parameter. ...
0
votes
1answer
43 views

Convert variable into function

Sorry if this is a duplicate, but I have a variable called H. H is some complicated function of ...
3
votes
2answers
290 views

Differential operator squared

I defined a one-dimensional momentum operator $\hat{p}=-i\hbar\frac{\partial}{\partial{x}}$ in Mathematica p = -I * h * D[#, x]& and I want to get the ...
0
votes
1answer
132 views

Patterns of function-arguments in expressions

I want a function that compares an expression with a specific pattern. The expression has always the following form: ...
0
votes
3answers
100 views

How to combine multiple functions into a single function, indexed bya new argument

I have a system of expressions (matrices) which correspond to increasing orders of precision in a theory. These expressions are quite complex (require about 40+ lines of code to produce) and are not ...
1
vote
2answers
130 views

Summing Over a Variable Number of Indices

I am trying to figure out the best way to include a variable number of indexes of summation in a program. For example: Suppose I want to define a function $g[n,s]$ that returns the sum ...
5
votes
2answers
419 views

Multiply each element of an array by another array?

I would like to multiply an array by each element of another array, and am having a lot of trouble finding a built-in or automated method of doing. Here is an example of what I'd like to achieve: ...
3
votes
1answer
187 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: ...
0
votes
1answer
60 views

Using Derivative with list in curly brackets

I'd like to make a formula for a sum containing Derivative where the number of arguments in the latter depends on an input parameter n. Also involved is a list ...
1
vote
1answer
78 views

How to define an n-variate empirical distribution function probability for any n?

I'm using Mathematica 9.0 to calculate the probability according to the empirical distribution function (EDF) of some sample data. Afterwords this is included in a maximization stage so I define this ...
0
votes
2answers
123 views

Defining Piecewise Functions in Modules

In short, my question is the same as my previous one except that everything is now wrapped up in a module. The relevant code I'm working with is: ...
2
votes
0answers
79 views

Function that assigns properties [duplicate]

I want to create a function that creates and assigns properties to a symbol. In theory this would behave similarly to the NonzeroValues property of ...
1
vote
1answer
77 views

Defining a function with global parameters

What I would like to do in Mathematica is something like f[x_] := a x g[a_] := NIntegrate[f[x], {x, 0, 1}] But then of course I get ...
0
votes
1answer
70 views

Create jacobian Function from a vector Function

This is related to this question and maybe this question. I wanted a function that takes an n-parameter vector function and outputs a Jacobian matrix function, also n-parameter. I think this works: ...
5
votes
2answers
344 views

Define a function with a function for an input

I want to create the functions $even[f]$ and $odd[f]$ which will apply the formula $even[f(x)] = \frac{f(x)+f(-x)}{2}$ and $odd[f(x)]=\frac{f(x)-f(-x)}{2}$ for an arbitrary $f$. I tried using ...
3
votes
1answer
127 views

String pattern matching in function definition

I have a function f and its downvalues. I want to code an extra downvalue for arguments of the form "part1:part2" I don't understand why ...
0
votes
0answers
41 views

Using Table[ ] vs using Do[Append [ ] ] [duplicate]

Is it generally better/faster to use the Table function over using Do[Append []]? For example, I have this piece of code: ...
2
votes
1answer
276 views

Defining Piecewise Functions [duplicate]

I'm having trouble defining piecewise functions. What I have so far is a function that outputs something in a suitable format for Piecewise: ...
5
votes
3answers
464 views

How to define the Poisson bracket in Mathematica

If $f,g$ are functions of the independent variables $\{q_1, q_2, ..., q_N, p_1, p_2, ..., p_N\}$, then the Poisson bracket is defined as: \begin{equation*} [f, g] = \sum_{i=1}^N \left(\frac{\partial ...
9
votes
1answer
223 views

How to define function that can change patterns

Given time series data as follows: data = {{{2011, 1, 13}, 10}, {{2011, 2, 14}, 17}, {{2011, 3, 15}, 20}, {{2012, 1, 16}, 30}, {{2012, 2, 17}, 40}}; ...
0
votes
1answer
107 views

Holding Input Windows

I am creating a Mathematica document which contains a list of proofs in various fields of Mathematics so that I can easily review whenever I would like. First, I create a large set I call 'proofs' ...
0
votes
0answers
35 views

Varying number of function arguments [duplicate]

I have a function of six arguments: ffit[q1_, q2_, q3_, q4_, q5_, q6_] := (a1*q1^2 + a2*q2^2 + a3*q3^2 + a4*q4^2 + a5*q5^2 + a6*q6^2) ...
7
votes
3answers
155 views

Checking through an expression

I am writing a code that manipulates expressions that contains functions with an arbitrary number of arguments. An example expression is ...
3
votes
1answer
106 views

How to Override the Head of a Symbol

I was wondering if it is possible to override the head of symbols/operators. As a motivating example if I run: Then Ket will be returned. But lets say I want Bob to be returned instead of Ket. Is ...
1
vote
3answers
106 views

Difficult parametric function

I've got this strange parametric function and I want to implement it on Mathematica. I know that I could use Excel and calculate it, but my database is quite large and I want to do some reproducible ...
2
votes
2answers
166 views

Find partial derivatives when the number of variables is unknown

The idea is that I have a defined function of $n$ variables. I want to find out $n$ and get partial derivation for each of variables, Suppose you have a function ...
0
votes
1answer
166 views

Please explain this code (contains Append, Do, Coefficient)

I am a graduate student using a past student's Mathematica program. Will someone please explain to me exactly what this piece of code is doing? Specifically the ...
1
vote
1answer
47 views

How to substitue local variables into expression with free variables?

I'm wondering how to do the following: expr = L + R; foo[L_, R_] := expr; foo[1, 2] (* L + R *) and have it substitute the function variables ...
-1
votes
1answer
74 views

How to specify a specific range for a loop?

I'm having trouble with setting up a particular range in a loop for my programming. Now I have a defined range of data (not continuous numbers) that needs to be applied in a loop. Since the aim for my ...
1
vote
2answers
266 views

Define function using variable list

I have a list of variables variables={a,b} and a list with values values={1,2}. I'd like to define a function using the ...
4
votes
2answers
308 views

Can Mathematica functions have static variables?

In C, one can have variables that are declared static. These are not re-initialized every single time a function is called. ...
1
vote
1answer
93 views

Possibility of evaluating the expression within a NestList at each iteration?

I want to rotate iteratively a triangle about the same point, increasing for each iteration the length of its side in the same proportion and change the color of its sides. I came up with the solution ...