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1answer
2k views

What are the Wolfram Mathematica NDSolve function methods?

What are the Wolfram Mathematica NDSolve function methods? I know that in Wolfram Mathematica I can specify solving method in NDSolve function, but I can't find a full list of available methods in ...
1
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1answer
420 views

Possible bug in Mathematica?

I'm running Mathematica 7.0.0 and came across this weird calculation (lines 1-14). ...
-1
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1answer
248 views

How to make Runge-Kutta for solving nonlinear ODE system in Mathematica

How to make Runge Kutta method for system of non linear equations in this Matrix form. Matrices A3, B3 and B4 are functions of matrix X3. Initial conditions are X1=X2=X3=X4=0 and system is here $$ ...
1
vote
1answer
165 views

Plotting a Function

How can one plot a three-dimensional plot of a differential equation system of the following to show the trajectories in mathematica: $x' = yz,~ y' = -2xz,~ z' = xy$ I tried using ...
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0answers
64 views

Using Fit on functions that use matrix calculation

I am struggling with using Fit to fit a (linear combination of a) list of functions, that are calculated using matrices. It seems Mathematica internally uses ...
0
votes
2answers
120 views

Create list of {x,f(x)} pairs

How can I do this in Mathematica: r=Range[0,20,0.13]; fr = HeavisideTheta[r]; data = somecoolfunctionsinmathematica[r,fr] So that data now is in the form useful ...
2
votes
0answers
371 views

Calculate periodicity in 1-dimensional array with noise

I have a 1-dimensional array with some integers, which are periodically increasing. Something like this (1 period here): ...
0
votes
1answer
71 views

A function of two functions that loses dependence on an argument

Say I have two functions: f[a_,b_]:=a + b g[c_,d_,e_]:=c + d - e And I define a third function: ...
0
votes
1answer
374 views

How to solve integral in Mathematica?

I need matrix H. G is working, but H is just derivative?? How to obtain? ...
0
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1answer
368 views

How to obtain integral in Mathematica faster? (Using parallel table?)

Hello Wolfram killers, Sasha was near, but how to obtain these two integrals? Ok 500 is to much for calculating, but 200, ok? ...
0
votes
1answer
227 views

How to obtain big matrix in Mathematica?

Can you help me how to obtain big but simple matrix in Mathematica? ...
2
votes
4answers
171 views

Simplify an expression to show equivalence

I am trying to simplify the following expression I have encountered in a book $\sum_{k=0}^{K-1}\left(\begin{array}{c} K\\ k+1 \end{array}\right)x^{k+1}(1-x)^{K-1-k}$ and according to the book, it ...
0
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2answers
264 views

How to solve this equation in Mathematica

How do I solve this equation in Mathematica? Using the NSolve command doesn't work! ...
2
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2answers
328 views

What is the “Mathematica” function for plotting a single variable inequality?

I was just wondering, how do I plot a single variable inequality in Mathematica? For example, we could use Wolfram Alpha for plotting an inequality like $x^3+4x+9 > 0$ and see something like this. ...
4
votes
4answers
3k views

Copy LaTex equations from Mathematica to Word directly?

Is it possible to use command copy as latex equations directly from mathematica file and paste in Word equation editor 2007/2010. Not to save like .pdf or .jpg! Alternative for web2tex or just this? ...
2
votes
1answer
386 views

Symbolic computation of the derivative of dot product of 2 vectors

If I have two vectors $a$ and $b$, whose components are time varying, for example $$a=[a_x(t), a_y(t), a_z(t)]$$ $$b=[b_x(t), b_y(t), b_z(t)]$$ The dot product of these 2 vectors can be expressed as ...
0
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1answer
160 views

Help needed with something like Matlab Solver or Mathematica Solver

I have never learnt to use the services (I have them though) but now I was given a massive amount of equations and I cannot really handle them without some solver tool, just plug equations and ...
3
votes
2answers
2k views

Function as parameter in Wolfram Mathematica

I want to define some basic functions known from "discrete analysis": $$I(f)(x):=f(x)$$ $$E(f)(x):=f(x+1)$$ $$\Delta(f)(x) := (E-I)(f)(x) = f(x+1)-f(x)$$ $$\nabla(f)(x) := (I-E^{-1})(f)(x) = ...
0
votes
1answer
754 views

Eigenvalues problem in Mathematica

The simple problem eigenvalues problem defined as: $A-(x^2)*B = 0$, where $A$ and $B$ are matrices. How to use command Eigenvalues[] in Mathematica to find $x$, ...
0
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1answer
2k views

Mathematica: Specifying assumptions/domains doesn't seem to work?

I frequently have trouble trying to place limits on Solve or Reduce using assumptions and domains. For example, this code: ...
0
votes
1answer
562 views

Mathematica - How to solve for the equilibrium?

So, I used Mathematica to create a basic SIR Disease model using the following equations: ...
0
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2answers
194 views

Solving ODE in Mathematica

I want to solve an ODE in the form $\{y'[t] == f[y[t]], y[2] == \{1, 2, 3\}\}$ using NDSolve in Mathematica, where $f: R^3 \rightarrow R^3$ is defined as follows, ...
0
votes
2answers
3k views

How to draw an parabolic path between two points

I have two sets of points and i want draw an parabolic arc between two points and also to find the intermediate points which the parabolic path is drawn.... In the above image you can see the curve ...
-2
votes
1answer
165 views

Precision and time of calculating the integral in Mathematica

1)How to calculate this integral, because I have some very small values (10^-20) in solution and values on this position in matrix should be equal to zero. If I can not do that with working precision, ...
-1
votes
1answer
626 views

NDSolve simple matrix problem in mathematica

I have a problem with command NDSolve in mathematica. If we have simple second order differential equation, it is easy to write code in mathematica. But if we have matrix problem (for example 4 ...
0
votes
1answer
2k views

How to make simple iteration in Mathematica

How to make simple iteration in Mathematica for this three equations and save $q$ for each step. If we define $q'=dq/dx$, $q''=dq'/dx$ we have two equations (1) ...
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0answers
431 views

How to make iteration for Newmark method in Mathematica 8

How to make iteration method for solving differential equations by Newmark method? There are just three equations which describe the Newmark method. I need q for time step for example 0.01. Also, for ...
1
vote
2answers
451 views

Mathematica 8 can not solve Eigenvalue problem

I cannot explain this eigenvalue problem. Both matrices are positive definite and symmetric, but some solutions are complex. But if it is matrices lower order, solutions are real. As I increase the ...
4
votes
1answer
235 views

Why does (Full)Simplify return terms with $0^n$ coefficients?

When I use Simplify[] or FullSimplify[], specifying domain reals, I get terms with $0^n$ as the coefficient. Isn't that always ...
3
votes
1answer
129 views

The limit of the expectation of the top half+1 order stats of $n$ draws of $X$ as $n\to\infty$?

Can anyone help me compute the limit of the average of the top half +1 of order marginal order distribution of $n$ draws from $X$, as $i\to\infty$? Specifically, the limit as $i\to\infty$ of ...
1
vote
3answers
323 views

Simple problem with pattern matching in Mathematica

I'm having trouble setting a pattern for simplifying a complex expression. I've distilled the question down to the simplest case where Mathematica seems to fail. I set up a simple rule based on a ...
4
votes
2answers
340 views

Independent High School Research

StackExchange Gurus! I'll keep this question short and to the point. I'm going into my senior year of high school, will have an independent research period, and have few ides of what to do during ...
0
votes
2answers
249 views

Plot graph with custom axes

How to plot graph with custom axes in Mathematica 8.0? e.g. use the axes $\frac1y$ instead of $y$ and $x^2$ instead of $x$? this is to implement Linear Law
0
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2answers
211 views

How do I transform an array into the Traditional Form with mathematica?

I am trying to set an expression in Mathematica that uses an array. However it is problematic to typeset this expression and still be able to use it. Here is my example: ...
0
votes
1answer
124 views

Poles placement problem

It is an equations of inverted pendulum. Example of controlling him with pole placement. $$ \text{eqns}=(M+m)x\text{''}[t]-m l \text{Sin}[\theta [t]] \theta '[t]^2+m l \text{Cos}[\theta ...
1
vote
0answers
182 views

Euler method on differential equation problem

I have this problem to solve. I want to compute the inclination of a plane $\theta(t)$ at every frame of a simulation given the following rule for its angular speed of rotation $\omega(t)$ $$ ...
1
vote
2answers
153 views

Taking advantage of linearity of integration in Mathematica

I want to evaluate an integral of form given below $$\int\limits_\alpha^\beta (f(x) + g(x) + h(x) + ...) dx$$ When I give it to Mathematica it takes forever to evaluate. But if I give it in this ...
2
votes
2answers
145 views

Computation of characteristic polynomial fails for me

For a matrix $A\in\mathbb{K}^{n\times n}$ where $\mathbb{K}\in\{\mathbb{R},\mathbb{C}\}$ the characteristic polynomial is defined as $$\chi_A(\lambda) := \text{det}(A-\lambda I_n) = \sum_{k=0}^n c_k ...
0
votes
1answer
211 views

Equation to find if a set of vertices form a concave shape?

i'm trying to get around the rule of only being able to form concave shapes in the SFML c++ library by forming the non-concave shape out of many concave shapes. What I don't know is the equation for ...
2
votes
2answers
312 views

Closed-form Expression for $\sum_{j=0}^{k-1}(2j+2)\sum_{i=1}^j \frac 1 {i^2}$? (problem with Mathematica)

I need to calculate a closed-form expression for $\sum_{j=0}^{k-1}(2j+2)\sum_{i=1}^j \frac 1 {i^2}$. This isn't particularly difficult, and I do it by hand pretty much routinely. However I found out ...
2
votes
1answer
424 views

How to use Mathematica to solve equations in a polynomial ring?

I am sorry. But I wonder whether it is fine to ask this question here. I need some help to solve some equations in a polynomial ring: Give the ring $\mathbb{F}_p [x ]/(x^2+x+1)$, where $p$ is a ...
2
votes
2answers
338 views

help with old Mathematica file

I am trying to solve a problem, for what I finally found a book what has some Mathematica files supplied, but I am stuck now as I cannot run the files. My problem is that I cannot run the program as ...
1
vote
2answers
203 views

Help need in Mathematica or Sage

I want to find the common positive solutions of two polynomials $f_{a,b}(x,y)$, $g_{a,b}(x,y)$ where $a,b$ runs from 0 to 1 with an interval 0.01. Let $(x_0,y_0)$ be a common positive solution. Then ...
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4answers
4k views

How to tell Mathematica about a constant?

Sometimes I want to ask mathematica to plot or calculate something without given a certain value for it .. For example I may want to ask mathematica to integrate $\int{a x} \mathrm{d}x$! How to tell ...
1
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1answer
389 views

Trying to pick a random point on sphere end up picking from a lune

I was inspired by this question to play around a little bit (its a weekend). I was pretty confident of my derivation and thought it might be nice to supplement it with a pretty picture. However, ...
6
votes
4answers
351 views

Best tool for verifying algebraic manipulations

Can anyone advise a tool that is very convenient for verifying algebraic manipulations step by step as I work. I too often waste hours dealing with a wrong formula because I missed a sign somewhere. I ...
0
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2answers
218 views

Mathematica Equation Solving

Suppose I wanted to solve the following for $a[1], a[2], a[3]$ in the Mathematica code: (a[1]+a[3])*t+(a[1]+2*a[2])*t^2=0 with $a[1] = 1$ where $t$ is just a ...
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0answers
521 views

Mathematica: How to convert scales to frequencies?

According to the transform $$w(u,s)=\frac{1}{\sqrt{s}}\int _{-\infty }^{\infty }x(t) \psi ^*\left(\frac{t-u}{s}\right)dt,$$ the frequency should be $f=\omega/(2\pi)=1/(2\pi s)$ (is it right?), where ...
1
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2answers
404 views

How to find endpoint?

How do you find the coordinates of endpoint of arc (pi + s) when the endpoint of arc s on the unit circle is (-sqrt (21)/5, 2/5)?
7
votes
4answers
1k views

Drawing a thickened Möbius strip in Mathematica

I would like to have Mathematica plot a "thickened Möbius strip", i.e. a torus with square cross section that is given a one-half twist. Ideally, I would like this thickened Möbius strip to be ...