# 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.

764 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 ...
125 views

### Cannot Plot Output of Solve

I'm trying to plot the output of the following function t2[x_] in ...
135 views

### correct usage of ParallelTable

I am trying to parallelize my script. Here is a MWE of how I have done it: ...
313 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 ...
155 views

### Change some option of a function when calling it [duplicate]

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 ...
325 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 ...
45 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: ...
117 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: ...
75 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 ...
54 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): ...
1k 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 ...
241 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 ...
553 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 ...
1k views

### Variable naming changes everything

Bug fixed in 10.0.0 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 ...
2k 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 ...
124 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 ...
813 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 ...
174 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 ...
1k views

### Mathematica plots a discontinuity in piecewise function that does not exist [duplicate]

I have the following function defined: ...
281 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 ...
532 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 ...
577 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 ...
1k 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 ...
108 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, ...
107 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 ...
800 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 ...
569 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 ...
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 ...
621 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 ...
837 views

### How to program a F::argx message?

How useful is it to program a user-built function in a package to produce a red warning message F::argx if you give the wrong number of arguments to that function? ...
102 views

### NMaxmize with a list of variables

I want to use NMaximize to find the maximum value of a function with multiple variables. The problem is I would like to set this up so the number of variables is only decided when the function sees ...