20
votes
Accepted
An efficient way to translate a triple for-loop from Matlab to Mathematica
Okay, let's focus on this snippet:
...
- 103k
18
votes
The Lotka-Volterra predator-prey model
The dimensional phase-space plot
The analysis of the predator-prey model is incomplete without the phase-space plot. So, here it is,
...
- 11.9k
12
votes
For Loop and Sum
Anyone asking you to write For loops in Mathematica for such a problem is a dolt. Nevertheless, here's how you might do that:
...
- 1,524
11
votes
Accepted
Particle moving on curve which is the intersection of a surface and a plane
You can use MeshFunctions to visualize the intersection. The following is one way to parametrize curve.
...
- 58.3k
11
votes
10
votes
Area of volume of revolution
r = ParametricRegion[{r Cos[ϕ], Sin[ϕ] r,
Sqrt[28 r]}, {{r, 0, 21}, {ϕ, 0, 2 π}}]
Area[r]
49/2 π (14 Sqrt[3] - ArcSinh[...
- 5,099
10
votes
9
votes
Plotting the solutions of $y' = -\frac{\cos y}{\sin x}$
This is just a suggested amendment to JasonB's answer. It wasn't clear to me that it deserves a separate answer, since it deals with side issues tangentially related to the OP's question.
It's easier ...
9
votes
8
votes
Accepted
Plotting Graph of Zeno paradoxes
You'll learn more trying to understand the following code than by programming silly Do[ ]s
...
- 115k
8
votes
Accepted
7
votes
Exercise using Sort
Using your code, let me make it clear by introducing an auxiliary function that sums the exponents in an expression
...
- 112k
7
votes
Plotting the solutions of $y' = -\frac{\cos y}{\sin x}$
I may not be understanding the question correctly, but if you wish to show the stream field under solutions, perhaps this is a method:
...
- 67k
7
votes
How can I make a pretzel shape using Bézier curves?
You can use a LocatorPane to edit the control points (at least in 2 dimensions) and see the curve change in real time:
...
- 35.9k
7
votes
Accepted
7
votes
Accepted
Strange determinant result
Det[{{0, 1/v, 0, -k12/v^2},
{0, 0, 0, -1/v^2},
{k12, k01, 0, 0},
{1, 1, 1, 0}}]
(* k12/v^3*)
Laplace
...
- 47.2k
7
votes
How to check whether Laguerre polynomials are orthogonal?
Integrate[LaguerreL[i, x] LaguerreL[j, x] Exp[-x], {x, 0, Infinity},
Assumptions -> Element[{i, j}, Integers] && j > i > 0]
0
...
- 378k
7
votes
Euler's method initial value problem — how should I plot the solution?
Euler's method to solve, plot, and compare to known solution:
$y^\prime = te^{3t}-2y, \quad y(0)=0, \quad 0 \le t \le 1. $
...
- 2,046
7
votes
Adams-Bashforth method implementation code review
There are typos in the code, and after minor correction we have
...
- 41.2k
6
votes
Check homework integration in Mathematica
As noted, Boole[] is the go-to method for older versions of Mathematica. Now, thanks to version 10's support for regions, one can easily enter
...
6
votes
Accepted
Poisson point distribution
This question was largely dealt with in the comments. I post this for illustrative purposes (but mainly fun):
The following shows use of PoissonProcess and its use ...
- 58.3k
6
votes
Accepted
6
votes
Accepted
Numerical approximation using trapezoidal formula
The error for the trapezoidal rule is
So in your case:
...
- 115k
6
votes
6
votes
Accepted
Rationalize number
Use Minimize with a condition that avoids the divergence to $-\infty$:
Minimize[{f[x], x > 5}, x]
{(-5 + 2 Sqrt[5] +...
- 6,755
6
votes
Accepted
Area of volume of revolution
It seems that f[x] is evaluating to a number. Probably you Set an OwnValues for ...
- 35.9k
6
votes
Accepted
Infinite While loop
The crux of the matter is how n is changed on each iteration.
Math
Consider a multi-digit integer $n = a_1 a_2 a_3 \ldots a_N$, where $a_k$ is the $k$-th digit of ...
- 7,750
6
votes
Accepted
Analyze stability of equilibria using Routh-Hurwitz conditions
There are "modified Routh-Hurwitz criteria" that work directly on the Jacobian matrix that I prefer and don't seem very well known (Fuller 1968). Here's a function I wrote that uses them for up to ...
- 19.4k
6
votes
How can I animate two beads each sliding on its own frictionless rail?
If there are no restrictions on r, x, then the solution is
...
- 41.2k
Only top scored, non community-wiki answers of a minimum length are eligible