# 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.

386 views

### Create a polynomial of a given degree

In Mathematica, how can I create a polynomial function in given variables of a given degree with unknown coefficents? That is, I am looking for a function ...
49 views

### Evaluating a list of randomly sampled triplets with a function of three variables

I'm new to Mathematica. I need to generate a list of 1000 triplets of random numbers {r, p, t}, so that 0 < r < 1, ...
65 views

### Apply If function to FoldList [on hold]

I have defined the following function: cpdz[c0_, m_,s_, r_, t_, n_] := If[c0 > 0, c0*(m*c0\s - (m - 1)*Exp[r*t/n]), c0*Exp[r*t/n]] for s I have a set of ...
68 views

### How to plot a function containing $\pm$ and unlimited solutions $n$? [duplicate]

I have $$y=n\pi\pm\arcsin(\sin(x)), n\in\mathbb{Z}$$ How can one define and plot such a function in Mathematica for multuple $n$ at the same time?
27 views

### Using set of lists in if function? [on hold]

I have the following function: a3[m_, C_, St_, Stt_] := If[C > 0, (m*C)/St*Stt, 0] now my input for C, St and Stt are different set of lists. So I tried to ...
25 views

### Nest function with an incremental parameter? [closed]

Usually, if we use the Nest[] command, it nests the function directly as in Nest[f,x,3] ...
27 views

### Pass list title as argument? [duplicate]

I have a function that works with a list and outputs it. Is it possible to also get the name of the list as an argument? Right now my code is ...
84 views

### Defining the Hirota operator

The Hirota $D$-operator (derivative) is mathematically defined as follows: $$D_x^n f\cdot g=\left.\frac{\partial^n}{\partial s ^n} f(x+s)g(x-s)\right|_{s=0}$$ An example of this operator acting on ...
94 views

### Recursion: How can i program this expression?

i have the following expression: Vt[EA_, V0_, Cm_, B_] := EA + (V0 - Cm)*B For EA and Cm ...
1k 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 ...
37 views

### Computing with recursion; how can I use values with lower indices without recomputing them? [closed]

I have to implement the following expression. V(tk+1)=max{(m×Ctk)/S_tk ,0} S(tk+1)+(Vtk-max{(m×Ctk)/Stk ,0} S(tk+1))×B(tk+1)/Btk How can I implement it so that ...
76 views

### Local modification of built-in command via UpValue

I have a computationally intense function f that returns a matrix. Sometimes only the diagonal is needed, which is faster to compute, thus there's a syntax for f to ...
44 views

### Why am I getting no visible plot of my function [closed]

I'm running the following command: ...
35 views

### Can you define “| |” to be the same as “Abs[ ]”? [duplicate]

When calculating the modulus of a complex number in Mathematica, the standard (and probably least-ugly) way of doing it is by using the Abs[ ] function. When doing ...
103 views

### How to make a custom function as inbuilt

I have a custom function like following: ...
609 views

### How do I get Mathematica to return a function call unevaluated?

How do I get Mathematica to return a function call (conditionally) unevaluated? I expect this may use the slightly-mysterious Hold function. As a toy example, ...
112 views

### Obtaining a Previously Constructed Function as Desired Output

I was playing around with some Generalized Trigonometric Functions defined as follows; ...
69 views

### Using Solve[ ] inside a Module

I want to use Solve[] inside a Module. If I make the variables solved for local to the module, they are treated differently than ...
40 views

### Defining a function when the variables do not appear explicitly in the definition of the function

I am trying to take the curl of a vector field which is the a product of a scalar field (Psi) and a coordinate vector, {r,Theta,Phi}. After taking the curl I want to calculate the magnitude of the ...
152 views

### How to save the caching produced in processing

As my this previous post.I get a custom function which can help me got some function contain a certain option.And I have put it in my "init.m" file. ...
159 views

### How do I get Series[] as a functional, rather than as an expression (i.e. to avoid the dummy variable)?

How can I write an equivalent to Series that doesn't require a dummy variable? Note that the series should be constructed before the evaluation point is supplied, ...
71 views

### Grouping/precedence for “/@” operator

This returns errors: {#[[1]],#[[3]]} & /@ {#[[1]],#[[2]],#[[3]]} & /@ {{"A","B","C"},{1,2,3}} Part::partd: Part specification A[[1]] is longer than ...
284 views

### How to split text without spaces into list of words? [duplicate]

What is the best approach to a problem like this in Mathematica? I can only manage this: ...
45 views

### Function with declaration of variables [closed]

Is it possible to create a function with declaration of variables inside. For instance ...
301 views

### How to check the validity of an option value

I have a user-defined function, func, which takes the following form: func[arg1, arg2, options] Here is the actual code ...
15 views

### Define a function as an evaluated integral [duplicate]

I have the following integral which I evaluate analitically ...
37 views

### Set a minimum threshold value for a function

I have defined the following function in Mathematica al[z_] := (a/((1 + a*(b/(2 Pi))*Log[z/Mz]))) (a and ...
51 views

### Line-crossing Algorithm Implementation (pt. 2) [closed]

This is a continuation of the problem I posted earlier with the line-crossing algorithm that I tried to implement in Mathematica. I took Kuba's suggestion, removing the underscore on everything ...
71 views

### Defined a function but it doesn't seem to work

I'm trying to implement the line-crossing algorithm on Mathematica and I seem to be having trouble getting it to work. More specifically, I would like to know what is causing the function to not ...
81 views

### Finding zero of nonlinear simultaneous equations [closed]

I'm trying to find the zero of nonlinear simultaneous equations defined in myfun1 and myfun2: ...
369 views

### Distributing function arguments with function compositions. How to compute $(f + g^2)(x) = f(x) + g(x)^2$?

Suppose I have two functions f and g. To compute $f + g$ evaluated at a point $x$, I know that one can use ...
56 views

### Defining a function that depends on the length of a number and the $n$-th digit

I have defined the functions F[i][x] for i={1, 2, 3}.. I want to write a number that has only the characters 1, 2, 3, and I want ...
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102 views

### How does a construct like i : func[arg_] := i = an expression using arg work? [duplicate]

Occasionally I run into a Pattern that looks like i:func[arg_]:=i= an expression using arg I have two questions on this: Can ...
70 views

### Dealing with a large number of optimizations performed with parameters read in from a CSV file

I have a large CSV file (1.5M rows), with each row containing a set of parameters that I need for an optimization routine in Mathematica. I'm hoping to import the data, run the computation, and then ...
55 views

### Problem using Nintegrate and NDsolve

I am going to use Nintegrate to integrate the result of NDsolve and also a Table. How I can ...
2k views

### How can I plot this spirally surface?

I would like to plot a surface that looks something like this sand spiral. But I really have no idea how. Ideally I would like to be able to express this as a function in cartesian coordinates. I'm ...
68 views

### Confusing alternative definition of a function [duplicate]

I saw a function defined something like the following: f[n_Integer][r, θ] = Sin[n r π/L] Cos[n r L π θ/4] My question is, why did my professor define the ...
50 views

### Doing vector calculus with element-wise defined formulas and arbitrary-sized vectors [duplicate]

Currently I am trying to make Mathematica handle vector expressions defined element-wise. For example, But I can find no way to do this. Every way I tried requires a fixed-sized vector and returns ...
109 views

### How to define action of derivative (D) on a user-defined operator f

I have a symbolic function (which is in fact an operator) f[expr, x] where the second argument is a local variable for f (kind ...
378 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 \$V=\...
5k views

### Creating custom functions with multiple arguments

I am hoping that this isn't a stupid question so feel free to vote it for closure. Google failed somehow. I want to define a custom function (more complicated than the usual ...
95 views

### How do I construct a Pattern with Alternatives and PatternSequence without getting Pattern::patvar messages?

Bug introduced 8.0 or earlier and persisting through 10.4.1 [CASE:3631078] In Mathematica 8 and 9, defining this rule: ...
31 views

### How to use OptionValue inside a pure function [duplicate]

I want to define a function with OptionsPattern as argument which returns a pure function using OptionValue: ...