474 views

Make mathematica treat $e_i^2$ as numeric

With NumericQ[symbol] = True, I can declare that a symbol is numeric. I want the expressions matching: $$e_{\text{i\_}?\text{IntegerQ}}^2$$ to be treated as ...
744 views

How can I ensure that I am constructing patterns in the most efficient way possible?

Inspired by this answer, I am interested to know if there are best practices or rules of thumb for constructing patterns, for example for use in function definitions (...
338 views

Searching linked lists that contain lists?

Following the advice I've read here and other sites, I've been trying to use the Mathematica equivalent of a linked lists... ...
743 views

Partitioning a list by recursion (Programming Paradigms via Mathematica (A First Course))

I am working through the course Programming Paradigms via Mathematica. One of the homework exercises for the section Recursion I: Passing the Buck is as follows: Use recursion to partition a list: ...
2k views

Count consecutive positions with the same value

I want to program a function that counts the successive positions with the same value: In[]= ConsecutiveValues[{1, 1, 1, 1, 2, 2, 1, 0}] Out[]= {4, 2, 1, 1} In ...
1k views

Built-in Mathematica data: are they cached? how to speed up the loading?

Mathematica has numerous built-in data for science and math. Every first call to a data function in a new Mathematica session will "re-initialize indices" (download the data). Is there a way to store ...
515 views

Find positions of duplicates that are neighbours

Assuming the following list {1,2,3,3,5,6,3} I would like to get the position of values that are next to each other and are duplicates. That is, the output should be {3,4}. Thank you for any help. ...
749 views

How to memoize a function with Options?

Consider the following modified fibonacci function: ...
449 views

Remove element from list and store it in variable?

In many programming languages there are functions that remove an element from a set while giving back that element. E.g. I'd like to have a function FetchFromStack ...
2k views

Simpler way to fill date gaps with zero values

One basic problem when working with data like sales and dates is the case where you don't have sales in all days, so you have to fill it to take information as average or to make a plot. See this toy ...
412 views

Generate PrimePower counting function

Is there a way to generate a counting function for prime powers - i.e. to create a similar function to PrimePi, but including prime powers. The following will, of ...
737 views

How to draw the image of a circle under the action of a transformation of the phase flow?

How to draw the image of a circle $x^2+(y-1)^2<1/4$ under the action of a transformation of the phase flow for the equation $\dot{x}=y,\ \dot{y}=-\sin x$? Here $\dot{x}$ means $dx/dt$. Any help or ...
223 views

Performance: Collapsing repeated contiguous rows & cols from a matrix

In this answer I needed to remove contiguous zero-valued cols and rows from a matrix, leaving only two of them in place, no matter what the original number was. I made up this code: ...