5
votes
1answer
72 views
Is it possible to save an interrupted computation?
I've got this really time consuming factoring problem. To decouple things a bit, I decided to start Mathematica using the command line interface (under screen).
...
2
votes
3answers
57 views
Problem with simplifying Sinc function
$Assumptions = x ∈ Reals && y ∈ Reals && a ∈ Reals && b ∈ Reals;
These work:
...
5
votes
1answer
65 views
How can I substitute something using only map?
For example, I have the equation
x^2 + y^2 == x*y
and I want to apply the rule
y -> s*x
I can do it easily by
...
0
votes
0answers
34 views
Generating partitions of a set with a specified size of the parts [duplicate]
I tried the following (inspired by the answer here)
myList = {a, b, c};
Needs["Combinatorica`"];
SetPartitions[myList]
and I got this answer,
...
4
votes
1answer
51 views
Preventing cell height adjustment when rotating 3D graphics
I have a large dataset of scattered x,y,z coordinates. I am trying to use ListPointPlot3D to identify outliers in 3D. This involves generating a plot and then ...
1
vote
0answers
16 views
Rationalizing Denominators with Radicals [migrated]
How do you rationalize this fraction:
1/(sqrt(n+1))
1
vote
0answers
55 views
Bounds on random number
I have a Markov Chain Monte Carlo code that uses a chi squared function to fit some data.
I am running into an issue now with getting unrealistic values for some of the free parameters
in the code. ...
0
votes
2answers
82 views
Visualize Plot of a function of 3 Variables using color and contours
I would like to plot a function of three variables, say for example:
$$f(x,y,z) = x^2+y^3+z^4$$
over $[-1, +1]$. I want my plot to use colors and maybe contours to make this visualization possible ...
3
votes
0answers
67 views
Using NDSolve for Integro-Differential Equations
I have a fairly complicated set of coupled non-linear integro-differential equations that I am trying to solve using NDSolve. The equations are:
...
7
votes
1answer
53 views
Creating a NearestFunction that returns an index
I use Nearest repeatedly for large data sets. For example
pts = RandomReal[{-1, 1}, {1000, 3}];
Nearest[pts, {0, 0, 0}]
I ...
1
vote
0answers
79 views
Performance in parameter estimation from ParametricNDSolve using varied initial conditions
I have 250 data points from a timecourse exeriment in a list, with columns specifying (1) time, (2-4) initial conditions, (5) absorbance reading. I want to fit 4 parameters (k1, k2, k3, k4) in a DAE ...
2
votes
2answers
43 views
Expanding Matrix Expressions
I want Mathematica to recognize that
A.(-B.C)+A.B.C = 0
Yet FullSimplify and the like leaves the expression as it is. How do I get around this?
4
votes
4answers
147 views
Unexpected behavior of Unevaluated
Maybe it is about time I read some proper text about the main loop. Maybe I should not care (so much) about Unevaluated (as Leonid suggests). But I think this is an interesting question anyway.
This ...
-2
votes
1answer
74 views
Mathematica output in ASCII or larger text size for the output?
I am trying to read the output of this code that has crosses, circles and spaces. For some reason, the output is in very-very small alphabets so I would like to get it in ASCII and/or in larger ...
-1
votes
0answers
61 views
Generate a list without braces? [closed]
Ultimately I want to plot a user-created function for many input parameters.
Plot[{P[1,k], P[2,k], P[3,k], P[4,k], P[5,k]}, {k, 0, 500}]
but I need to generalize ...
4
votes
2answers
106 views
Why is this parallel evaluation with Dispatch[] so slow?
Can you efficiently parallelize this? The parallel versions are much slower than the sequential version, and I'm not sure why. Does SetSharedVariable allow ...
1
vote
1answer
55 views
How to enumerate multisets
Given the eight-element set {1,2,3,4,5,6,7,8}, I would like to enumerate all multisets (subsets with repetition) of size n, where n >=3. For example, with n = 3, the sets {1,1,1}, {1,1,2}, ..., ...
2
votes
1answer
57 views
NDSolve with vector function
(Possible duplicate yet I still can't understand.)
Basic 2D revolving around origin:
...
2
votes
3answers
134 views
Using ImageTransformation[] with a lookup table
I need to transform images by ImageTransformation in a time critical application. Therefore I precalculate a lookup table lut of ...
0
votes
0answers
33 views
1
vote
1answer
66 views
How to crop graphics outside PlotRange with Show? [duplicate]
Is there an option or method to prevent Graphics from being displayed outside the PlotRange region?
The problem is illustrated ...
1
vote
0answers
35 views
A Symbol with Subscript and Superscript as an Axis Label
I am trying to have the symbol $\epsilon_{9/2,4}^-$ as the axis label in a graph in Mathematica. First problem is that: when I use Subscript[$\epsilon$,9/2,4], 9/2 changes to $\frac{9}{2}$ (which I ...
0
votes
2answers
58 views
Plotting points and functions in one graphic
I have this plot:
Plot[{0 x, -x, x, -Sqrt[2 - x^2], Sqrt[2 - x^2]}, {x, -3, 3},
PlotStyle -> {Purple}]
Now I want to do the following. I want to plot the ...
0
votes
1answer
82 views
TextRecognize with crosses, circles and spaces results into oddities, why?
I am investigating this answer here about detecting crosses and circles with TextRecognize. I tried to solve this problem here by directly using the builtin command TextRecognize but it does not work ...
0
votes
0answers
52 views
Problems with ListDensityPlot
I have the errors in one quantity $x$ in a List form as $(\Delta x,z)$, being $\Delta x$ the error and $z$ the value in which $x$ has the respective error. I want to make a density plot of the errors ...
1
vote
0answers
39 views
CDF Player: MathKernel.exe uses a lot of memory
When I run this CDF document http://x6174x.blogspot.pt/2013/04/bankroll-growth-simulator.html on my desktop, each time I press "Run again" the Task Manager shows that the MathKernel.exe process ...
7
votes
2answers
101 views
How to simplify an expression with special functions to zero
The following is a well-known Bessel function identity:
$$J_{-n}(z)=(-1)^n J_n(z),\qquad n\in\mathbb Z$$
To check this, I used the following code and the result is as what I expected.
...
3
votes
0answers
26 views
Behavior of $PreRead in Kernel
I am interested in making a simple accounting style line calculator that allows me to interact with it something like this:
...
1
vote
0answers
74 views
How can I use mathematica to price Amazon's S3?
Amazon provides a html form for its price model of cost per gB usage. I'm trying to figure out the formula behind it, is there a way to use Mathematica to generate data from the form and then ...
2
votes
2answers
93 views
How to select elements from a 4D Array?
I am very new to Mathematica (first time!) and I'm already having troubles with arrays. I basically have a 4D tensor, that is a matrix (call it M) which has for ...
2
votes
1answer
61 views
Normalize the PlotLegends and z values for two DensityPlot
I'm trying to compare two DensityPlots:
...
0
votes
0answers
4 views
permutation and abstarct-algebraShow that there does not exist a permutation α in S4 satisfying (1 2)(3 4)α = α(1 2 3 4)? [migrated]
Show that there does not exist a permutation α in S4 satisfying (1 2)(3 4)α = α(1 2 3 4)?
0
votes
2answers
59 views
List Plot 3D the same colour scale
I have a transient problem of pressure disipation. I want to plot severals 3D plot but I have a problem with colours.
Case:
One of my ListPlot3D presents pressure ...
0
votes
0answers
77 views
Monitor the list for changes
I wrote a function to monitor the list of variable. What it does is if the variable in list change, the changed variable will be separated from others. check the function and output
...
16
votes
1answer
298 views
The Orbit and Perigee of the Flamsteed comet
Historical context
This year we have the 330-th anniversary of the Battle of Vienna - one of the great formative events of European history, it took place on September 12, 1683.
Kara Mustafa, Grand ...
1
vote
1answer
67 views
Integration of a rational function
I am trying to solve the following rational integral (I got assistance here):
$$\int_{-\infty}^{\infty}{\frac{a+x}{b^2 + (a+x)^2}\frac{1}{1+c(a-x)^2}}dx$$
where $\{a, b, c\}\in \mathbb{R}$. I would ...
-1
votes
0answers
40 views
Evaluating the different calculations
I am a new user. I wonder that either there is possible to evalute different calculations at the same time in Mathematica or not? Can i share the kernels for different calculation at same time?
0
votes
0answers
13 views
(x^2 + 5)^2 - 15(x^2 + 5) + 54 = 0 [migrated]
I got the square root of 14 and 11 but the answer book states that these answers are wrong. Can someone help me? I used this formula to find the individual roots
x = - p/2 + or - √ (p/2)^2 - q
0
votes
0answers
14 views
Solve √(2x-5) - √(x-1) = 1 [migrated]
Although this is a simple question I for the life of me can not figure out why one would get a 2 in front of the second square root when expanding. Can someone please explain that to me?
Example: ...
3
votes
1answer
46 views
Use Initialization Cells to open a CellGroup
I would like to use "Evaluate Initialization Cells" to open a CellGroup in a notebook. However, the following code doesn't work if placed in an initialization cell:
...
2
votes
0answers
61 views
Reducing exponential inequalities fails
I am quite stumped by this problem :
Reduce[ N^(x-y) <1 && N > 0 , x, Reals]
gives the expected result
...
-1
votes
1answer
88 views
Solving for variables in a series of nonlinear equations [closed]
I have a nonlinear expression in five variables. I want to use Mathematica to solve for three of the variables. I have a series of points giving values of x an y and I am trying to solve for a,b, and ...
0
votes
0answers
45 views
Generating partitions of a set [duplicate]
Is it possible to get Mathematica to generate all possible partitions of a set of objects?
(..or equivalently if it can be made to do the cumulant expansion or at least the Gaussian special case of ...
1
vote
1answer
109 views
Concerning ShowLegend in Mathematica
I found a code for Mie Scattering from 2007, written for Mathematica.
I have edited it quite a bit, since there are package definitions that we don't need, etc.
But I am having difficulties ...
1
vote
0answers
84 views
4
votes
0answers
75 views
When using NMinimize[…,Method->“DifferentialEvolution”] is an “iteration” different than a “step”?
Hopefully this question has a simple answer. I have the following bit of code:
...
1
vote
1answer
95 views
How do I operate on a set of ordered pairs? [closed]
I have a calculation that will give me a lot of ordered pairs. For each such pair in a list, I want to square the elements and add them together. Here is an example of the kind of list I have
...
2
votes
0answers
82 views
Solving homogeneous Fredholm Equation of the second kind
I am trying to solve a homogeneous Fredholm integral equation of the second kind, i.e.
$\lambda y(x) = \int\limits_a^b e^{i[\phi(t)+k(t-x/M)^2]} y(t)\,dt$
where $\lambda$ is the eigenvalue (to be ...
3
votes
0answers
78 views
Mathlink and multithreading
In order to make my computations faster I have developed a C/C++ application calling Mathematica kernel and performing many operations using Mathematica functions for equation solving.
Now I want to ...
3
votes
1answer
145 views
White noise $\eta(t)$
How to make a random function $\eta(t)$ to insert in a differential equation for NDSolve?
Edit: example: to solve equations like $\frac{dx}{dt}=\eta(t)$
