All Questions

0
votes
1answer
612 views

Extract variable and coefficient from equation elegantly

I have quadratic equation like $eq = x2-7*x5^2$ and vector $xx=\{x0,x1,x2,x3,x4,x5,x6,x7,...\}$. I need to do some nice calculations which will give me coefficient $k=7$, $y=x2$ and $x=x5$, so that ...
0
votes
0answers
116 views

Implicit function: derivative of piecewise function that has a FindRoot in one of the pieces

I have a piecewise function that has as one piece the result of a numerical approximation, like in the example below: ...
0
votes
2answers
179 views

Find *all* numerical solutions to cosine based equality

To help with https://astronomy.stackexchange.com/questions/11456/ I'm trying to find all numerical solutions to: 5.20427*Sin[0.529699*t] == Sin[2*Pi*t] Since the period of the first function is ...
0
votes
1answer
842 views

Combine Plots into a single non-rasterized Graphic with no spacing [duplicate]

Suppose that I have two plots, pl1 and pl2: ...
0
votes
1answer
78 views

How can I show constraints on parameters in 3D plot? [closed]

How can I exclude a region in a 3D plot? I have done it for a Density plot, but for the 3D case, it seems difficult to exclude a region (with a certain relation between two main parameters). In fact,...
0
votes
0answers
170 views

Initiating another Kernel?

How can I start a separate kernel to do other work, while I have Mathematica working on a problem that requires lots of computation time? I have a program that must be run for many hours, preventing ...
0
votes
1answer
137 views

Resulting list of ComponentMeasurements

I detect a single bright object in an image with the following code; ...
0
votes
1answer
161 views

Inverse of a multivalued function

I try to get the inverse of a simple function like x^2,x≥0. Still, when I use InverseFunction Mathematica gives me back -(y^0.5) ...
0
votes
1answer
2k views

Plotting a piecewise function [closed]

I'm having trouble plotting the piecewise function below. The only way I can replicate this function is using ...
0
votes
1answer
75 views

Large Community Clustered Network Formatting

I created this visual of a network using: CommunityGraphPlot[adjmatrix, VertexLabels -> "Name"] It looks like this: Is there a good way to expand the nodes ...
0
votes
2answers
256 views

Solving the 3D Poisson equation on the surface of a cube using a relaxation method

The code below is from another question asked by someone else about solving the 3D Laplace equation for truncated octahedron in a cube matrix, How to solve Laplace equation in 3D?. I wanna know, how ...
0
votes
2answers
205 views

Drawing a large set of Graphics3D cylinders provided a set of cylinder specifications in a list

I'd like to draw a large number of 3D cylinders using Graphics3D. My list specifying the cylinders has elements that look like the following: ...
0
votes
0answers
525 views
0
votes
2answers
357 views

String quotes elimination

I'm trying to import a .csv file that contains some points which are geo-positions, but the import gives me the points wrapped in quotes. Is there any method to get them as pairs of real numbers? I'm ...
0
votes
1answer
543 views

How can a package use a variable of a notebook?

I have defined a function g in a package. It is: g[x_]:=x/.t->3 Now I work in notebook with the command: ...
0
votes
1answer
83 views

Finding surface fit on 3D graph that have different data length

I have a question to find the surface plot on the list of data with different data length. Each of the sample a different length, how can I combine all these data and find the best fit surface for ...
0
votes
1answer
107 views

How to solve 2D PDE with a constraint?

As related to the 2D+1 PDE problem, if now I would like to solve the stationary solution which satisfies $\partial_t u(t,x,y)=0$. Or equivalently, $-y\partial_{x}u+\partial_{y}\left[a y+b sin(x)u+...
0
votes
2answers
191 views

Why does Integrate[] return an expression with 'True' in it?

I am running Mathematica 10 on Windows 10. I'm trying to analytically evaluate a definite, principal value integral: ...
0
votes
0answers
68 views

How to obtain all minima? [duplicate]

If you Solve an equation, you obtain all solutions. But If you NMinimize a function, you only get one minimum. The question is:...
0
votes
2answers
363 views

Manipulating a damped oscillator plot - plot does not show

I was trying to make an oscillation plot that could be manipulated depending on the value of $\beta$. The differential equation is below, and when I just plot the solution, it turns out to be the ...
0
votes
1answer
1k views

How can I use nonlinear model fit with multiple variables? [closed]

I have a data set with four entries. the first three entries correspond to variables in the fit x,y, & z. The fourth entry corresponds to the function value. I am trying to fit this data to a rate ...
0
votes
1answer
864 views

What is the correct way to use NIntegrate inside the FindMinimum function?

I'm having minor issues with the FindMinimum function when using NIntegrate inside. The functions work perfectly well but I get ...
0
votes
0answers
101 views

FiniteElement and NDSolve won't work

I need to solve a system of DE's in 2 dimensions over time, The problem is that mathematica complains when I have a boundary condition of the same order as the differential order of the DE's, so I ...
0
votes
1answer
45 views

Give Mathematica points in the XY plane and find equation that generates them

I am finding the minima of a 2D cubic periodic function by "brute force", i.e. looking for the (x,y) positions where the both the x and y derivatives are 0. This returns a list of points, in this ...
0
votes
1answer
66 views

Using multiple solutions from equations in further calculations, part II

First: This is a follow-up question to my question here, since I wasn't specific on what I really wanted. Condider the following code: ...
0
votes
1answer
48 views

How to apply RenameFile to a CloudObject

As the documemtation in Details and Options: RenameFile works on cloud objects, changing their cloud file names but not their UUIDs. I think this sentense imply the ...
0
votes
1answer
165 views

plot randomly oriented lines

I want to create the following graphic: A set of line-elements are randomly oriented in planes parallel to xy-plane. In addition, on each plane the drawed line-elements should not cross each other. ...
0
votes
1answer
662 views

“Moving” plot of a point moving in circular motion, in 3D

Maybe this is a tricky one! I want to have a 3D plot in Cartesian coordinates of a point moving in a circular orbit around x,y,z = 0. where the circular motion is only in the x,y plane. Has anyone ...
0
votes
0answers
104 views

Mathematica creates a huge eps file [duplicate]

I use the following code (based on the responses in my recent relevant questions) in order to generate randomly distributed unidirectional cylinders in a cylinder of elliptical cross section. ...
0
votes
1answer
100 views

how to generate vertical scale on both sides of the plot? [closed]

Usually on a plot the vertical scale is on the left, and the horizontal scale is on the bottom. How to make the vertical scale appear on both left and right, and similarly the horizontal scale on both ...
0
votes
1answer
842 views

Pull Constants outside of integrals

I would like Mathematica to pull constants outside of an integral: e.g., $\int_0^t f[t] g[s] dt \to g[s] \int_0^t f[t] dt$ This has previously been discussed at replacement rule to pull independent ...
0
votes
1answer
3k views

Discrete Fourier Transform: help on how to convert x axis in to the frequency when I have a set of data samples [duplicate]

I have a huge data set (400000 sample) and when I plot them ListLinePlot[Au4, PlotRange -> {All, All}] I used the following code to Fourier transform it <...
0
votes
1answer
166 views

Industrial Level Applications. Recipe for mixed notation of equations set

I am working with large (linear) equations set within Mathematica in numerical notation. For example, set from 4056 eq. is solved for a second, no more. There is no doubt, result is great. But even ...
0
votes
1answer
196 views

Variable order in output

I have two questions about editing my output in Mathematica. I want the variables to be to the right of the fractions with the parameters. Update ...
0
votes
2answers
707 views

How to solve this FindFit::nrlnum:

the following code show error message FindFit::nrlnum: "The function value {6.71759 -9.36268*10^-8\ I,6.51797 -8.42641*10^-8\ I,6.31789 -7.49014*10^-8\ I,6.1179 -6.55387*10^-8\ I,5.91794 -5....
0
votes
1answer
61 views

Import create evil invisible characters when import txt including ellipsis:“…”

I'm using Mathematica10.0.2 on Win7 suppose I have a txt file named test_Import_characters.txt(http://pan.baidu.com/s/1hsvy6xQ) which contains two lines of string example(copied from http://...
0
votes
1answer
150 views

Floating point arithmetic bug caused by Table[]

I was doing something fairly ordinary and noticed something I can't, for the life of me, explain. For context, I wanted to take make a function that takes an array of data like the one below, then an ...
0
votes
1answer
304 views

Plotting stability Mathieu diagram

Please, can someone offer me some help with the code which generates those last three graphs illustrating the three regions - first/conventional region, second/"r.f.-only" region, third/"intermediate" ...
0
votes
0answers
42 views

How to transfer the list of parameters values into With [duplicate]

In the following case: With[{x=1,y=2},Print[x+y]] the values of x and y are declared in ...
0
votes
5answers
148 views

Find optimal integer solution to linear equation (Wolfram Alpha)

I'm sorry if this is potentially off topic, but I posted this question at the Math SE and they pointed me here. Both SE sites have a tag for Wolfram Alpha, but maybe you guys are better equipped to ...
0
votes
0answers
126 views

How to implement a Cube 2: Sauerbraten octree?

I found this image of subdividing a cube based on octree model for the game "Cube 2: Sauerbraten octree". How can such an octree subdivision algorithm can be implemented? I also need a generalized ...
0
votes
1answer
153 views
0
votes
1answer
2k views

How to show legend in a combined plot of many lists,

I am having trouble with adding a legend to a plot. The example I discuss here is simpler than my real problem, but describes it well. I have a vector, called X with dimensions (100 x 6). I use the ...
0
votes
1answer
89 views

Dynamic number of parameter fits in Mathematica

I am trying to learn if in Mathematica one can perform fits of analytic functions that are expanded and written as power series. In particular, we can consider the following generic form: $$ f(B,x) = ...
0
votes
1answer
2k views

Finding the intersection of two graphs [duplicate]

I'm having difficulty with finding the intersecting point of two graphs. Here is what I have done so far: Plot[{8*n^2, 64*n*Log2[n]}, {n, 0, 100}] which produces ...
0
votes
1answer
208 views

Colors on a 3D curve not working

I'm having troubles applying colors to a simple 3D curve plot. Here's the code : ...
0
votes
2answers
134 views

How to get the correct answer of this expression with Minimize? [closed]

I want to find minimum value of the expression $$P = 13 x^2 + 12 y^2 + 22 z^2$$ such that $x y + y z + z x = 1$. I tried ...
0
votes
1answer
182 views

Compiling function solving for the smallest eigenvalue of a matrix

I am trying to speed up my code, which many times finds a lowest eigenvalue of a Hermitian (symmetric, real) matrix. Using a small 2x2 matrix as an example, this works: ...
0
votes
1answer
569 views

Heun's method for a system of ODE's [closed]

I need to solve a system of two ODE's using improved Euler's (Heun) method. Can any one help as I am pretty bad at Mathematica. This is what I've come up with so far ...
0
votes
1answer
252 views

Maximum and minimum plotted on a curve

Through code: ...

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