https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230366
The Lotka-McKendrick model is a demographic model that represents the way a population changes over time due to fertility and mortality. For an age-specific population density \( u(a, t) \), and a total ...
asked by Pillsy https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=531 12 votes
answered by Chris K https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=6358 9 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230429
I’m a newbie with Mathematica, I know it’s a basic answer, but I can’t solve the problem on my own. I have the following equation reflecting insect aggregation at low population densities (taken from ...
asked by Vefhug https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=74729 10 votes
answered by xzczd https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1871 17 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230622
I need to improve a pattern or switch an approach. It is best described by an example For a hierarchy/order given by a list e.g.:
order = {1, 2, 3}
and a list:
asked by Kuba https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5478 9 votes
answered by Leonid Shifrin https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=81 9 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230484
Background Let’s say I want information (e.g. bulk modulus or space group) on an element
or chemical compound that isn’t available via e.g. ElementData[]
asked by Sterling https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=61736 6 votes
answered by Sterling https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=61736 6 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230383
I’m trying to solve a simple system of second order PDEs with Mathematica 11.1. Here is the system:
asked by C. B. https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=74734 6 votes
answered by bbgodfrey https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1063 3 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230650
My mind is a bit cloudy and I can’t quite pinpoint the pattern here that will allow me to write an elegant piece of code to build the following symmetric matrix of for a given size ...
asked by QuantumDot https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=2048 5 votes
answered by kglr https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=125 4 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230613
I have a section in my notebook devoted to unit testing, since I’m not comfortable to use the built-in system. I’d like to evaluate the entire section by button click. But I get lost in the notebook ...
asked by infinitezero https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=31036 5 votes
answered by Kuba https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5478 5 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=6669
I understand Mathematica can’t assign the results of a Solve to the unknowns because there may be more than 1 solution. How can I assign the 4 values of following result to variables?
asked by stevenvh https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1450 56 votes
answered by Artes https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=184 34 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=18598
For my Calc III class, I need to find \(T(t), N(t)\), and \(B(t)\) for \(t=1, 2\), and \(-1\), given \(r(t)=\{t,t^2,t^3\}\).
I’ve got Mathematica, but I’ve never used it before and I’m not sure how to coerce ...
asked by a98 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5605 30 votes
answered by Artes https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=184 43 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=15023
The basic multivariable Taylor expansion formula around a point is as follows:
\[ f(\mathbf r + \mathbf a) = f(\mathbf r) + (\mathbf a \cdot \nabla )f(\mathbf r) + \frac {1}{2!}(\mathbf a \cdot \nabla ) \]
asked by matheorem https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4742 58 votes
answered by Jens https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=245 65 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=11350
I received an email to which I wanted to respond with a xkcd-style graph, but I couldn’t manage it. Everything I drew looked perfect, and I don’t have enough command over ...
asked by Amatya https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=2039 615 votes
answered by Simon Woods https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=862 474 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=222184
I am interested in benchmarking numerical integration methods and am trying to develop a wider set of difficult multivariate examples. For my particular methods, I only want to look at non-negative-...
asked by ben18785 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=19278 6 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=66969
Here is a start. I’m looking for a nice way to draw it.
asked by matrix89 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5379 24 votes
answered by Bob Hanlon https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9362 21 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=148
Is it possible in Mathematica to get a step-by-step evaluation of some functions; that’s to say, outputting not only the result but all the stages that have led to it? If so, how does one do it?
asked by Cydonia7 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=44 125 votes
answered by J. M.’s discontentment https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=50 105 votes
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230550
I am trying to solve the equilibrium equation \(\text {DIV } \mathbf P(\textbf {u}(x,y)) = \mathbf {f}\), where \(\mathbf P\) is the stress tensor defined by \[ \mathbf P = \mathbf F + (1-\det \mathbf F) \] asked by rmk236 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=74782 1 vote
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230520
I am trying to solve something like Fick’s Law using NDSolve
\[\frac {\partial \varphi }{\partial t}=\frac {\partial ^2 \varphi }{\partial r^2}+F(r,t)\] Subject to a ...
asked by UranylTrioxide https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=74775 1 vote
https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230425
I have written the following piece of code:
asked by Mr. Mister https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=74745 2 votes