Questions on writing non-trivial programs in Mathematica. Do not use this tag for questions on plotting/graphics or for questions on doing mathematics with Mathematica, where the focus is more on the math than the program.

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252 views

How do I slice an image of size “width × height” in n² pieces of size “width / n × height / n”?

Background: What I want is to make a jigsaw from an image. (A simple one where the pieces are polygons.) I have the following strategy in mind. Create a set of polygons and assign images (or just the ...
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1answer
101 views

How to write or extend operators like $*\!\!*$

I'm stuck on trying to define simplification rules for NonCommutativeMultiply, much like ExpandNCM found in Documentation Center, under Applications. For example, I'd like ...
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1answer
85 views

Functions behaving weirdly

The following code f[k_, n_] := Sum[2*(1 + Sum[f[k - j, n - m - j], {j, 1, k - 1}]), {m, 1, n - k + 1}] f[4, 7] f[4, n] gives the output: ...
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1answer
77 views

Ways to protect certain parts of expressions

I am currently working on a quantum mechanics problem where I try to find equations that relate different states of a many-body system. The states are described by sets of pairs of integers, like ...
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2answers
130 views

How do you apply an algorithm individually to an array with many graphs

I have and array with many graphs to which I want to apply an algorithm (below) to each graph in an array that contains all my graphs. ...
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2answers
609 views

Plotting an orbit using first principles [duplicate]

I am fairly new to Mathematica, but I am trying to plot an orbit of the Earth around the sun using the equation: $\quad r(t+dt) = (2 - G*M*dt^2/r^3)*r(t) - r(t-dt)$ I need to break this into ...
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1answer
240 views

Programming- cryptography

I have defined the following function in Mathematica to get a SET OF m SETS (these sets are the codes {p,q,d,e,n} for the ...
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2answers
383 views

Plotting in the “Manipulate” function - simple coding

Hello Mathematica community, my name is Preston! I have a real quick question that should be easy to answer. Alright, so for a research project that I'm involved it at my university, I need to ...
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2answers
122 views

how to generate repeatable Unique streams?

I need to label some data in arbitrarily nested ragged lists, with a stream of unique labels. It's very convenient if the labels are consecutive integers, starting at ...
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1answer
227 views

Calculating mean of multiple stochastic processes and setting a lower threshold

Thanks to “Rod Lm” I got some very nice input for the following problem. My intention is to simulate within a Manipulate function a given number of possible stock ...
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1answer
118 views

How can I find the row differences of a matrix?

How can I compute the row differences of an m x n matrix to obtain an m-1 x n matrix; that is, given how do I obtain
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2answers
290 views

Inputting two arrays for a module in Mathematica

I am relatively new to the Mathematica enviroment and not sure where I am going wrong. I have evaluated the question and understand it, but dont know how to exactly create a module for it. The ...
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1answer
254 views

How can Time be made to go backwards?

I would like to make a countdown timer, but cannot find a reliable method to make the DateList[] function reverse. The not so robust code for the Digital Clock with the display of seconds follows: ...
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1answer
42 views

Question about transforming a list of rules

Consider the following list: ...
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1answer
73 views

Help with getting an output from some calculations

I entered the following from @Rahul's answer in "Help with finding the point(s) inside a closed shape with the highest average ray length?" below my post. He told me I should enter his data one input ...
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1answer
74 views

How to find line error in init.m file?

I have been changing my init.m user file. It runs fine, but I do get this error below. What does it mean by line 55? What constitutes a line? Are lines separated by "," or ";" or both? Or is it ...
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2answers
162 views

Code for Newton's Method [closed]

I'm trying to write a program for finding the root of f(x)=e^x+sin(x)-4 by Newton's Method but I'm instructed to not use the built in function and write the code from scratch. I'm pretty new to this ...
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2answers
111 views

How to write a loop

I try to create a table which will describe traffic paths at a crossroads. Instead of using copy-paste repeatedly, I would like to write a loop. For example: ...
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1answer
202 views

How to properly use conditionals inside NDSolve

Currently I am working with Mathematica to learn the program, and I'm confused what exactly is wrong with this code. ...
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1answer
66 views

Implicit region is not “valid” in ParamatricNDSolveValue function?

I am trying to solve a geometric problem with relation to my Schrodinger equation and its boundaries. Here is my code: ...
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1answer
257 views

How would I obtain a list of column names in a Dataset?

I really love the addition of Dataset to Mathematica. I would like to write a basic utility function that exports a Dataset to Excel. Is there a way to get a list of column names from a Dataset?
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2answers
65 views

How to get the outermost command evaluated first?

I have an expression like ToString[Stuff[...]]. I plan on having the Stuff[...] be manipulated as a string according to the output of other parts of the program. The problem is that Mathematica tries ...
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2answers
137 views

Using conditionals to check if LinearSolve found a solution

Is there some way to check if LinearSolve found a solution using conditionals in Mathematica 9? I need to solve a large number of linear equations, but I am only interested in the cases where there ...
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2answers
68 views

Changing a tag when one function is passed into another using UpValues

I have two complicated functions f[x,y] and g[t]. Before the main evaluation code in ...
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1answer
72 views

Elements of a List according position in axis

({{a, b}, {c, d}}) a, b, c and d are Lists of 300 length. Their first 4 elements must specify their position in the column (1 column, 2 column, etc) and the ...
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2answers
120 views

Clearing arguments passed to a Module

Is there a possible way to clear the arguments passed to a module to release some memory. I believe that arguments passed to modules are passed by value rather than pass by reference. e.g. I have the ...
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1answer
206 views

Read expression from Mathematica via Mathlink C++

This is a simple C++ program to send an expression to the_Mathematica_ Kernel and get its response. ...
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1answer
74 views

MLEvaluate() Function Gives Error

I am trying to link my C++ program to Mathematica Kernel. I am trying to use the MLEvaluate() evaluate but I receive an error while compilation. My codes are as below: ...
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2answers
127 views

How to return matching sublists or empty list

How to return matching sublists or empty list m1 = {{1, 0.5}, {2, 0.4}, {3, 0.1}}; m2 = {{1, 0.5}, {0, 0.4}, {0, 0.1}}; Commonest[Join[m1, m2]] out: ...
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1answer
329 views

A problem on generating convex hull

For example, I typed the following: ...
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1answer
277 views

Making an animated simulation without procedural loops

I'm still new to Mathematica and this is the first time I've wanted to do something more complicated than plotting and changing parameters of mathematical functions. I want to make a simple ...
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1answer
176 views

How can I import sound from within a Manipulate expression?

I want to import sound from a file, record, and import sound. ...
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1answer
928 views

pointer like operations in mathematica and evaluation control

I would like to create a data structure of the type "header[pointer]" where pointer would point to a list. I will shown on an example how I'd like this to work, and where the problems are. ...
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2answers
307 views

Checking equality with ComplexInfinity and testing whether a function is (mathematically) undefined

This seems ridiculously basic, but I cannot find anywhere explaining how to do it. If you evaluate certain undefined functions like 1/0 or ...
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1answer
188 views

What is the new command for AffineMap?

AffineMap was present in Mathematica version 4. What is the equivalent command in the current version of Mathematica?
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1answer
115 views

Draw from HistogramDistribution with ParallelTable

I wanted to check something, but ran into troubles using HistogramDistribution in combination with ParallelTable. The code does the following: Compute a HistogramDistribution of some sample and use ...
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1answer
44 views

How to apply hermite InterpolatingPolynomial?

I found that to do hermite InterpolatingPolynomial I need to write: InterpolatingPolynomial[{{{1}, 2, 3}, {{2}, 6, 7, 8}}, x] however,i need to apply it on a ...
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1answer
202 views

How can we accommodate arbitrary Unicode characters in symbol names?

I understand why Mathematica doesn't the support the [ character in symbol names, but it should be escapable in some way, like non-printable characters are in ...
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1answer
48 views

How to reference StringExpression named parts from a package without full Context path?

I have a long StringExpression in a package returned by a function. There are some named parts in the expression that I would like to reference when I use the ...
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1answer
105 views
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82 views

How to define a number of infix operators with predefined relative precedences

Reading a number of questions about infix operator notations I want to ask if somebody could reimplement the problem below in a simpler way, say modifying ...
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1answer
49 views

Why this isn't a valid argument? [duplicate]

I am having truble understanding why F1 produces an error, since both time and velocity are the same kind of object: ...
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1answer
58 views

Emulating Case Pattern replacement

As most regular users, I have developed utility functions complementing the Wolfram language for frequent tasks. In particular, I have variations on Cases (see ...
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1answer
135 views

Perceptron: Do loop not returning a value

I am trying to write a function that finds a simple best fit line for some data (Perceptron algorithm). Sadly it returns no output at all. Here's the code below: ...
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1answer
93 views

Hypothesis Testing and Formatting Output

I am trying to write a function that tests hypotheses and gives me a nice table but I can't. I need forum's help. For example, I have the following data ...
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1answer
312 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 ...
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1answer
104 views

How to understand the extensional usage of Flatten? [duplicate]

Recently, I have been reading Mathematica program that written by many advanced Mathematica user, like Mr.Wizard, J.M., Kuba,etc to improve my programming capacity In the On generalizing Partition[] ...
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2answers
718 views

How to define a function or procedure that includes multiple steps?

I would like to define a procedure or function that takes as input an integer, s, and gives as output two nested lists. I have written code (shown below) that does this for one particular value of s, ...
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1answer
145 views

Scope of variables within a Manipulate expression [duplicate]

I have a problem in defining the local variables. I have this code: ...
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2answers
199 views

Avoid making repeated Random Integer in different iterations

Assume following code : Do[ i1 = RandomInteger[{1, 5}]; i2 = RandomInteger[{1, 5}]; While[i1 == i2, i2 = RandomInteger[{1, 5}]] , {k, 1, 4}];` This ...