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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0
votes
1answer
48 views

How to define InterpolatingFunction on a variable set of points?

I would like to define an InterpolatingFunction to which data points are transferred as a parameter, e.g.: ...
22
votes
4answers
338 views

Is there a GraphicsPrimitiveQ (or a complete list of Heads of graphics primitives)?

For various reasons related to workflow associated with creating figures for journals, I am creating functions that will accept graphics primitives and a set of options and spit out a ...
4
votes
2answers
162 views

Subset-type function construction

This is probably a very straightforward thing I am missing, and probably also a duplicate(!), but I can't for the life of me think how to do this cleaner. I want to achieve what ...
4
votes
2answers
57 views

Is it possible to match a sequence with multiple heads without using Condition

Suppose I have: expr = Times[2, a[x,r], a[y,1], c[z,0,0], d[w,m]]; If I want to match a sequence of expressions with the same head ...
4
votes
1answer
89 views

Pertubation series of given equations

I would like to define a function that does the following. If I have an equation, for example: $$f(x)+[1-f^2(x)]+f^{\prime\prime}(x)+f(x)\ f^\prime(x)=0$$ and I am given a value for $f$ to expand ...
0
votes
0answers
75 views

How to change the built-in function? [duplicate]

As you can see,the original Differences will get {} when your parameter is a list with one element just. Differences /@ {{1, 2, ...
4
votes
2answers
106 views

Finding the smallest starting number producing a Collatz sequence of length 125 which ends with a value > 4

I'm supposed to do a Mathematica function that selects the smallest number not less or equal to 4 after 125 iterations. I am not good at coding, so some help/advice would be awesome. My code so far. ...
0
votes
1answer
51 views

Cumulative function definition and plotting [closed]

I'm quite new to Mathematica. I have an issue defining cumulatively a function. Let's say I have a waveform f[t] , and I want to create a function with many copies ...
0
votes
1answer
63 views
32
votes
4answers
2k views

Using pure functions in Table

I need a table with the elements made of pure functions and list elements. This is a simplified example: I need a list as: ...
0
votes
2answers
99 views

Gradient of interpolated 3D data in mathematica 9

tt = Flatten[Table[{x, y, z, btot[x, y, z]}, {x, -1, 1, 0.1}, {y, -1, 1,0.1}, {z, -1, 1, 0.1}], 2]; ff = Interpolation[tt] Till here it is working fine as it is ...
4
votes
1answer
87 views

How to Return $Failed symbol in a MakeBoxes context?

Three months ago, I asked a question about How to build a function object like the built-ins? Today, I used a solution proposed by István Zachar ...
8
votes
4answers
302 views

How to inject unevaluated list of Unique into a RuleDelayed?

I am writing a function that constructs a rule which has Unique[] in the RHS. Here is a simplified segment of code ...
0
votes
1answer
46 views

Results of a function are different when the function call and subsequent statements are evaluated one line at a time

I have some code that I am porting from VBA to Mathematica. The original code processes data on an Excel spreadsheet. In Mathematica, I find it convenient to replicate the Excel spreadsheet data ...
7
votes
1answer
133 views

Can one specify a “computed optional value”?

I would like to write a function with an optional argument, which if absent should not be a default value, but rather a computed value. What I mean is the following [warning this code does not work, ...
8
votes
1answer
103 views

How to make `D` apply chain rule on user-defined symbols as it does on `Dot` and `NonCommutativeMultiply`

I have my own version of Dot called mydot, and it behaves quite similar to the built-in version in that it represents the non-...
6
votes
3answers
280 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 <...
1
vote
2answers
123 views

How to make function accept list of rules as an argument?

Considering the list of rules: r= {"a" -> "1", "b" -> "2", "c" -> 3, d -> 231, "e" -> 1.25}; I want to have a function ...
12
votes
4answers
215 views

How to define a function that is Listable for some but not all arguments?

I want to define a function f[x,y] that is Listable for only the first argument, not the second. If we use ...
3
votes
1answer
81 views

Finding all Spanish words with given vowel patterns

I'm trying to implement a function using DictionaryLookup that does the following: Uses a Spanish dictionary Lists and counts of all words where the 5 vowels ...
2
votes
1answer
35 views

Expanding/printing function with constrained arguments [duplicate]

Let's say you have a function $ f(t) = t, \text{ for } t > 0,$ declared in Mathematica as f[t_?(# > 0 &)] := t; How do you print that function? I ...
1
vote
1answer
95 views

Continued fraction with different numerators [duplicate]

In Mathematica, is it possible to form the continued fraction of the following formula? $$ f = a_1+\cfrac{b_1}{a_1+a_2+\cfrac{b_2}{a_2+a_3+\cfrac{b_3}{a_3+a_4+\cfrac{b_4}{a_4+...}}}} $$
8
votes
4answers
209 views

Identify the independent variable in an expression [duplicate]

Suppose that you write something like this for your students. This is just the beginning of something I would like to write to help them with the formal definition of a limit, but I am puzzled by the ...
22
votes
3answers
487 views
2
votes
2answers
132 views

Plotting a function defined to be infinite over a sub-domain [duplicate]

I'm trying to plot the following function with the constraints shown, $$f(x)=\begin{cases} \infty \quad x<0 \\ A\,x\quad x\ge 0 \end{cases}$$ However I can't work out how to show this in ...
7
votes
4answers
103 views

Problem with handling a factor of $1$ in pattern matching

I am trying to implement the creation and annihilation operators $\hat{a}$ and $\hat{a}^{\dagger}$ of quantum mechanics with the following code, but alas, there is a problem with the pattern matching ...
5
votes
1answer
125 views

How to make my fuction return a step count

I am new to mathematica, and I have this 3d random walker program which runs with a fixed (given) amount of steps. What I want it to do is to run forever but stop when two walkers collide (aka have ...
7
votes
3answers
94 views

How to organize expression by symbols (like Collect), but apply different functions to each coefficient

I want to mimic the functionality of Collect[expr, {vars}, func], but with the following modification: The function f that is ...
11
votes
5answers
871 views

Reverse Polish Notation

Is there a way to evaluate a string containing RPN in Mathematica? SE thinks this question is too short, so let me expand on it. Do you know of any function, that provides the following functionality?...
2
votes
1answer
130 views

Pattern condition involving multiple arguments to a function

I can define conditions on individual arguments to a function: f[a_List/;condition(a),b_List/;condition(b)]:=(...) I am wondering if there is a way of declaring ...
3
votes
1answer
88 views

How to inject segments of code into functions defined by SetDelayed [duplicate]

I need to define a set of functions that are written in terms of common but lengthy expressions. To effect this, I want to inject abbreviations for such expressions into the RHS of ...
1
vote
0answers
45 views

Rescale large numerical factors in rational functions

Given a rational function $$ f(x_1,x_2) = \dfrac{r_1 x_1^2 + r_2 x_2}{r_3 x_1 + r_4 x_2}, $$ with $r_i$ arbitrary real or complex numbers, is there a built-in function to get Mathemtica to rewrite as $...
9
votes
1answer
151 views

How to make a function to analyse a sentence?

I have two lists: grammarNonterminal = {{VP,{V,NP}},{NP,{D,N}},{S,{NP,VP}}} sentence = {{D,"the"},{N,"man"},{V,"hit"},{D,"the"},{N,"table"}} I want to make a ...
2
votes
1answer
126 views

How to constrain the range of a plot of a function to satisfy an inequality?

Given the function f[x_] := x^2, how can I plot f[x] over the range where f[x] >= 10 and <...
0
votes
1answer
30 views

Solution of a function that is in a variable [duplicate]

If I want to get the solution for a simple function, e.g. a^x, I can use: a = 2; Function[x, a^x][2] However, if I have the function in a variable, I can't get ...
3
votes
1answer
95 views

Evaluate Limit only if both directions(sides) are equal?Ex: $\lim _{x\to 0}\left(\frac{1}{x}\right)=DNE$

I want the limit of a function to only evaluate if both the left and right hand side are equal. For example $\lim _{x\to 0}\left(\frac{1}{x}\right)$ doesn't exist(two sided limit). However, the right ...
6
votes
2answers
290 views
2
votes
2answers
46 views

Deciding whether the return value of a function is defined based on its input [duplicate]

I have been met with the following problem: I have defined the following: myFunc[e_Integer]; That means, if I call: ...
4
votes
2answers
92 views

Defining arbitary Derivatives of functions

If I have two functions like these f[a_,b_] and g[a_,b_]. Lets say ...
0
votes
1answer
88 views

High-order functions and interactive objects

I have been developing Mathematica code to interpret LaTeX code, extract formulas and apply various Mathematica operations (e.g. Simplify, ...
1
vote
1answer
96 views

ClickPane and InputField entry in a Manipulate

By clicking at a point on the slope field for an ode, a solution is plotted through that point. Additional clicks produce more plots; the plots are saved in graph ...
5
votes
3answers
213 views

Make own rule for multiplication

I'm new to mathematica, so I still cannot use it properly. I want to do symbolic programming. My question is : is there any way to define our own multiplication. Suppose $a,b$ are arbitrary variables,...
7
votes
3answers
84 views

TagSetDelayed on a function with a delayed value

I'm trying to automatically optimize cases when the user evaluates Length[returnsList[x_]] to instead use returnsLength: ...
1
vote
1answer
95 views

Using a table as a variable in a function

I have a bunch of arrays and need to extract specific rows and columns of these that obey certain criteria. So for one table I'd do like this ...
1
vote
1answer
39 views

Please explain this pattern/Message related issue and help with finding workaround

I attempted to clean up my code and also add messages to functions if they are called with wrong arguments. This introduced some error which I tracked down to the following: ...
3
votes
4answers
193 views

Pack Solve results into a vector

I am currently using a really easy function to get the eigenvectors of a corresponding eigenspace: ...
2
votes
2answers
93 views

Function where variable is integration bound

Lets say I have a function of the form: $f(T) = T^4 \int_0^{1/T} \frac{x^3 dx}{e^x-1}$ This is an example of the situation I am describing not a unique problem. I want to define it as a numerical ...
2
votes
1answer
46 views

combine two definitions into one [closed]

Suppose I have two definitions of a function such as ...
1
vote
1answer
85 views

Define recursive function over two indices

I have $x_i=(i-1)/50$ for $i=1,\ldots,51 $. Given a function $ f(x) = x^2 $, I want to find $y_i^k$ given by \begin{eqnarray} y_i^1 &=& f(x_i) \\ y_i^{k+1} &=& \max\left[\frac{y_{i-1}^...
2
votes
1answer
1k views

Inverse gradient operator

I found a nice paper about inverse vector operators here. I have successfully implemented a Mathematica function for most of them, however I can't figure out how to do inverse gradient (page 7 in the ...