# Questions tagged [programming]

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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### Seeking Wolfram Mathematica Techniques for Detailed Step-by-Step Solution of Integral Equation Transformation

Hello Mathematica Community, I am working on a mathematical problem where I need to transform an integral equation into a simpler form using Euler's Formula and the Error Function. My current ...
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### How to define a custom operator/rule to convert $f(t-a) g(x-t-b)$ into $f(t-a) g(x-a-b)$?

I want to define a rule or an operator such that I can have an input like Sin[t-2]Cos[x-5](z-x-t-9)^2 //.someRule to get the output ...
1 vote
203 views

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### Generate random arithmetic test with MMA

I have been trying for a long time to generate a question test where operations with 2 rationals appear printed. Can someone help me with the code? shows the following errors. a) The options appear ...
1 vote
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### More generic version of Variables [duplicate]

What's the best way to extend Variables to work on expressions that are not polynomial? IE, the following returns {x,y}, but I ...
95 views

### Caching result of evaluation in the notebook?

Sometimes I have a cell which takes a while to re-evaluate, but the result is quite small. It would be nice to have an easy way to "cache" some computations by embedding the result in the ...
119 views

### Turning expr+replacement rules into a function which automatically applies replacement rules?

What's a good pattern to turn expression+replacement rules into a function which automatically applies these replacement rules? IE, I'm finding a common pattern in my code, have some programmatically ...
44 views

### Nest n-times a multi-variable function with only one of the variables being updated with previous function value

I have a function y1 of three variables, x, y, and z. (y1 also depends upon f1 defined previously). I would like to Nest or interate, such that on the nth iteration, the y1's 3rd variable, z, will be ...
189 views

### Select applied to multiple objects

I have a matrix and want to extract rows according to some criterion. Then I have other matrices and want to extract the same rows. For example, if my criterion is to find rows where all the ...
1 vote
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### How to fit data known up to a proportionality constant using NonlinearModelFit? [duplicate]

Referring to my last question here Problem with NonlinearModelFit in the case of ODE I am still looking for your help in solving the data-fitting problem where the data are only known up to a ...
1 vote
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### Problem with NonlinearModelFit in the case of ODE

I am asking for your help for fitting a nonlinear ODE to data which are unknown up to a multiplicative constant k. So the constant k appears both in the data, and in the model, where it ...
211 views

### How can I get rid of Background from a String?

For explanatory purposes I have marked parts of a string with different backgrounds. But this string is part of some Mathematica expression, which processed. My program worked fine before I added the ...
68 views