# 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.

602 views

### Piecewise smooth rectangle pulse

I am wondering how to create a single rectangle pulse with nonlinear riding and falling edges on both sides. I don't know whether it is better to do it piecewise or to mathematically transform the ...
48 views

### How shortening argument test when declaring functions?

When defining some functions which depend in many arguments sometimes we need to include question Q constraints to diminish processing time. My question is simple, there is a way to shorten a long ...
240 views

### A better way of handling Module output?

I am sure this has been asked before in a way or another. I need to Save or DumpSave some symbols that contain the result of ...
184 views

### Quantize a real-valued function?

I'm wondering if there's a built-in way in Mathematica to take a function whose output values are continuous, and quantize it to produce a step function. For example, I have the function ...
230 views

### How to assemble and disassemble a function into steps

I've watched many programmers (both novice and expert) write functions in Mathematica and have observed a common behavioral pattern. This pattern has many elements that would be automated and thus ...
104 views

### Best practices for breaking up functional blocks?

Say I have a main function that does some job, and I'm only interested in the final result of ans, i.e., the local functions are not important and produce no side-...
131 views

### Why doesn't Thread work in this case?

The following function is supposed to pick the element of the list with highest weight, i.e., with Thread [f[{{a,1},{b,2}}]] it should make the variables ...
96 views

### How to test a condition for a list and output all the expression that is true?

Suppose that I have a list lis={x-y,x+y,x*y}; and a function f[a_,b_]:=#/.{x->a,y->b}& I want to output all the ...
237 views

### Composition of Multivariable function

I am trying to compose functions of xleft, maybe like xleft[xleft[f]] or even higher order. And here is my function: ...
284 views

### How to make a function from body with variable number of arguments?

Suppose I have an UNKNOWN function, which generates formulas with given number of x[i]. ...
91 views

### Count the number of element repeats at various distances

I have a function of x: f[x_] := Abs[Extract[list, x + n] - Extract[list, x]] I then apply this: ...
255 views

### How to define a nested function like this?

For example, I want to calculate the limit of $\frac{1}{1+\frac{2}{1+\frac{3}{1+\ldots}}}$. So I want to define: $f(1)=1$ $f(2)=\frac{1}{1+2}$ $f(3)=\frac{1}{1+\frac{2}{1+3}}$ Then I calculate ...
178 views

### Understanding NestList with multiple functions

General question For a function f[n, a], where a is a list and n is a whole number, what is ...
210 views

### Can't use my own discontinuous coefficient within NDSolve

I want to evaluate the pendulum's motion with changing equilibrium state given by eqilValue[t]: ...
177 views

### Using a held option

Woud there be an elegant way to use a held option ? For example if I need to pass by reference several variables but I don't always need all of them, it can be useful. For example if I want to append ...
225 views

### Recursive functions taking list arguments

I wish to create a function that takes lists (e.g. {plus,plus,minus,0,minus,plus}) and uses the input list to calculate a corresponding value using a set of ...
82 views

### Help creating a simple function

Can someone help me to create a function. The truth I'm new in Mathematica and I don't understand well the way functions work in I. I need a function that animate some rectangles according to a curve ...
45 views

### Linear function on strings using UpValues

I have two functions Sup and Sdown that take a string of letters with allowed characters ...
335 views

### Optimizing Chi-square distance between two distribution

I want to program the chi-square between two distribution Xu and Vu with length N. This function is defined as below: Xu and Vu are real and positive. ...
128 views

### Defining a function that prints both the name and value of a variable defined locally within the calling function

To save time when debugging with Print statements, I'd like to define a function -- call it PrintVal -- that prints both the name and value of a variable defined locally within the calling function. ...
272 views

### Error: in the part assignment is not a symbol [duplicate]

I am trying to set part of a Doubly-indexed list aInitialPopulation to cNumHeg. Specifically I am trying to set the 3rd part of the list aInitialPopulatiom[[cNodeNumber]] to cNumHeg. My (attempted) ...
64 views

### What are the applications of using functions whose heads are also functions?

I noticed that it is possible to construct something like f[x][y]. Displaying this in TreeForm indicates that this expression ...
596 views

### Variable that changes itself

I am trying to store a boolean value into a variable with the additional property that the value changes each time the variable is called. ...
136 views

### How to sum values in the list that belongs to same week

I need to sum values that belongs to same week. For example, I have the list x with one column and n rows. Format: ...
61 views

### Searching for symbol except within subexpressions with a particular Head

I would like to write a searcher like FreeQ that looks for a Symbol (or Head) in an ...
104 views

### How do I localize an assignment to expression (instead of symbol) within scoping construct?

Is it possible to localize an assignment to an expression (defined via UpSet) instead of a Symbol within a scoping construct? ...
33 views

### How to make Expand work right in a function definition?

This works just fine: Derivative[n_, 1][g][x_, v_] := D[g[x, v], {x, n + 2}]/2 + D[D[g[x, v], x]^2/2, {x, n}]; h = Expand[D[g[x, v], {v, 3}]] I would like to ...
197 views

### Parentheses for negative integers

Trying to standard create prime factors presentation, but can't seem to remove the parentheses: ...
334 views

### How can I call the R-programming packages in my Mathematica?

I am trying to call the R-programming package called highfrequency in my Mathematica so that I can use its function rCov. I ...
43 views

### Mapping also for one element (or telling it how to do so if head got changed)

Some code generates a polynomial, and has the form: expr = Plus[a[i],b[i],c[i],d[i]] I need to apply f to each term. To do ...
96 views

### How to form a variable from matrix elements

I have matrix with n rows and 2 columns, say m = {{x11, y12}, {x21, y22}, ..., {xn1, yn2}. Now, I want to form three new variables for example: ...
105 views

### Plotting a function in {X(Y),Y} space

The code below generates some data and defines a function f[x,cb]:=NMaximize[expr,x] that upon being evaluated returns: {function value at max $x$,the function maximizing $x$}. ...
187 views

### How to track Part of Symbol or How to symbolize Parts of Symbol without copying data

Let's create simple function: SetAttributes[h, HoldFirst]; h[data_] := Dynamic[Grid[data], TrackedSymbols :> {data}] test = RandomReal[1, {2, 2}]; h[test] ...
281 views

### How to get “Signature” of each element of “Permutation” output

I need to sum over all possible permutations, multiplied by the Signature of each permutation of a given list of symbols. But, I don't know how to determine the <...
120 views

### How to create a complex variable from dated list values

Can anyone help me to construct a variable "PI" from values of variable x. Variable x represents a group of two time series rj and ri on equal dates(joined two dated lists with states).Variable x have ...
211 views

### What is the correct syntax for using a radio button to set values to be used elsewhere? (restated)

Here is my question, restated - I want to be able to choose the values for a complicated function from a set of alternatives values that I have gathered. The function requires several input values, ...
211 views

### Returning the 3-dimensional vector from a skew symmetric matrix

I'm trying to write a function that takes in a skew symmetric matrix and returns the corresponding vector. When I write the following code, it works when I leave it as variables, but it does not work ...
67 views

### Fast functional method for multiplying duplication numbers in a large list

Consider a list of symbols: mySet = {a, b, b, c, a, b, c, d}; I would like to form the product of duplication numbers. In the example above, I have 2 ...
74 views

### Unprotect fails the first time, works on second pass [duplicate]

I am redefining some of the standard math functions. I know this is dangerous, so I am trying to be extra careful. (For instance, in the redefinitions, I make sure to only match a custom head) The ...
324 views

### How to define multiple functions using a for command

Let's say I want to plot 10 graphs of those following functions. Since they are recursive functions, I cant make a table with 10 different initial conditions because Mathematica stores each value ...
398 views

### Extracting coefficients from a power series

I have a function defined explicitly as a power series: $$\sum_{n=0}^\infty{T_n}\frac{x^n}{n!}=\frac{\frac{x^3}{3!}}{e^x-1-x-\frac{x^2}{2!}}$$ and I would like to extract the coefficients $T_k$ as $k$...
156 views

### using memoization with conditional statement

I would like some advice about the use of memoization in conjunction with conditional statements. Let me try to explain my problem: I am constructing a function depending on a number of parameters. ...
178 views

### Mapping a function of the form matrix[[row,column1;;column2]] over a list

I want to create a list of lists of values by mapping values[[row, col1;;col2]] over a list like {{r1,c1,c2},{r2,c2,c3},... } to ...
227 views

### Defining Associated Stirling Numbers of the Second Kind

First, I'm new to Mathematica. I spent my undergraduate programming with Maple, and my computer crashed and I lost it. Fortunately, my university offers free Mathematica downloads to students, so ...
325 views

### How to write complex function definitions at run time?

(Posting as a self-answered question to share a technique I discovered) In a certain project, I have many function definitions in which all parameters should be optional and come with default values. ...
803 views

### How can I evaluate only a single step of a recursive function?

Let's say have a simple recursive function for the Fibonacci sequence f[0] := 1 f[1] := 1 f[n_] := f[n - 1] + f[n - 2] but I want to see how it will expand in a ...
210 views

### How to re-parse (or re-map) character '.' to user-defined function

The default behavior of the character . between two non-numeric characters is to be interpreted as the infix of the Mathematica function ...