Mathematica Definition and 1000 Threads

i want to solve a large system of coupled differential equations but i get this error NDSolve::nlnum: i attach the notebook in zip format. what is the problem? thanks

Hi everyone, Is it possible to order a list of (x,y) coordinates in Mathematica by x, then y? I currently have a number of data files in which there are 5 columns: x, y, area, circularity, radius. I would like to order the list by x and y coordinates while keeping the rows intact. Thank you

hi how can i solve a system of Integro-Differential Equations in mathematica numerically or analytically? thanks

In the pic, I wonder what Mathematica can't do. :-)

Hello, I have this equation as attached, I need to integrate with respect to 'phix' from 0 to ∏/2. I have been waiting for the solution for one hour. Does it not have closed-form? Could someone please point the problem. Thank you so much.

Does anyone familiar with a convenient way in Mathematica to define a case function such as: y(x)=\left\{\begin{array}{c} x \\ -x\end{array}\begin{array}{c} x>0 \\ x<0\end{array} \right. ? Thankes, Omri

Hi All, I am trying to solve a set of coupled non-linear algebraic equations. I'm doing this using the LinearSolve fcn of mathematica and an implementation of the Newton-Raphson method. One of the issues I'm having is that I need to tell mathematica that one of these variables,let's say x...

I calculated a binocular disparity \delta of two points, see also this topic, and got the following formula: \delta = Arctan(\frac{f}{D + d}) - Arctan(\frac{e}{D}) - Arctan(\frac{a - e}{D}) + Arctan(\frac{a - f}{D + d}) The assignment now says: Choose a = 6.5 cm, D = 40 cm and e = 3.25 cm...

Hi all, I'm just a beginner with mathematica, and I tried to plot the solution of the following equation \frac{d}{dx} (x^2 \frac{d y}{dx})=x^2 e^{-y} with boundary conditions y(0)=0, y'(0)=0 Using the following mathematica code: NDSolve[{D[x^2 y'[x], x] == x^2 Exp[-y[x]]...

Hey all, I'm very new to Mathematica, so I'm looking for some help here. I'm writing an elementary program using a "For" loop, and getting this error message: "Sum::write: Tag Plus in i-1 is Protected. >>" Any ideas what might be wrong? Thanks!

Hi guys. So I got this assignment, where I have to create my own function, which can calculate the determinant of any n x n matrix. The general formula we've been given is (recursive formula): det(A) = Sum[n,i=1] (-1)^{1+i} * a_{1 i} * det(A_{1 i}) where n is the length of the matrix...

How in the world do you take the square root of a matrix in Mathematica? All the ways I've tried haven't worked... Thanks!

I'm trying to use Mathematica to solve a system of equations based on coordinate transformations and Lagrangian mechanics. The code follows here. However, when the system of equations is run, Mathematica never reaches an answer nor does it give an error, it simply runs infinitely. This is for a...

I have a pde set as following: parameters: γ, ω, α, β, c, η variables: z,t; x,y want: S = S(z,t;x,y) A = A(z,t) ∂S/∂t = -γ*S - i ω*A*exp{-i*[(-θ-α*t)*x+β*t*y]} [∂/∂t + (1/c)*∂/∂t] A = -i η*∫∫dxdy S*exp{i*[(-θ-α*t)*x+β*t*y]} The integral range is angle:(0,2Pi), radius: (0,R) How to...

Hi. Can someone explain to me how to sort a Series so that the terms are in increasing powers of the exponent? For example the code: myseries = Normal[ Series[Sqrt[1 - w], {w, 0, 5}]] /. w -> 1/z produces 1-\frac{7}{256 z^5}-\frac{5}{128 z^4}-\frac{1}{16 z^3}-\frac{1}{8 z^2}-\frac{1}{2...

Hi, first of all I am new to Mathematica.(Mathematica v8.0.0) The Problem: I have been having some issues with one particular integral lately: I need to perform InverseFourier over a region of certain frequency and set the result as a function of time for later use...

hi suppose i run Two notebook and in each of them i have matrix A and Constant B and a function C in each notebook these things have the same name. if in notebook 1 i assign B=10 then in notebook 2 B is 10 too , which is not my desire. how can i define these constants and matrices and...

Hello, I recently learned about the Fourier Series and how it can be used decompose a periodic signal into a sum of sinusoids. I can calculate all the coefficients by hand, but I wanted Mathematica to do that for me. I attempted to write a code, and it does give the desired output. I...

Hi everyone. I've been using basically a whole day on two trivial Mathematica issues, so I'm finally going online for help: 1. Is there any simple way to define the gradient as a new function as such? My try: Clear["Global`*"] f[u_] := x[u]*y[u] gradf[u_] := D[f[u], {{x[u], y[u]}}]...

Hello Im new here, I hope I'm not disturbing anyone. Following this guide below, I am trying to find two 2. order differential equations, one for q1'' and one for q2'', describing the movement of the double pendulum. I have no problems with the mathematics, but when the guide tells me to...

Hi, I am trying to solve a second order nonlinear eqn which is y''+3y'=1/(y^5), y'(0)=0, using mathematica. When I type DSolve[y''[x]+3*y'[x]=(1/(y[x])^5) ,y'[0]==0,y[x],x]; I get "second-order nonlinear ordinary differential equation" as a result. I don't understand what mistake I am making...

Probably a basic Mathematica question but after trying a few things I'm stumped. I have a table with some x values and a range of data that are dependent on those values, call them a(x), b(x), c(x), etc. So the table looks like { {x1, a1, b1, c1}, {x2, a2, b2, c2}, {x3, a3, b3, c3}, etc. }...

hi when i run a heavy computation on mathematica in the same time even if i want to calculate 2+2 , mathematica does not calculate it until calculating of heavy computation finishes. why? another problem is that when i do a heavy computation and obtain results , after closing mathematica...

The potential inside of a uniformly charged sphere of radius R is given by \frac{Q}{4\pi \epsilon _{0}}\frac{1}{2R}(3-\frac{r^2}{R^2}). Please help me on how to plot this equation in Mathematica

Hi, I'm quite new to Mathematica, and I've been trying to use it to solve some PDE's numerically, and I eventually end up with a really large matrix I have to find the solution for. I was think the calculation would go by faster if I could take the precision of the numbers down. I think...

Hi, I solved a differential equation using Mathematica using NDsolve, I get some solution, but I only know how to plot it in Mathematica. The problem is that I need the data - numbers - and I want to work with then a finally make the graph using gnuplot. Is there any way how can I cat...

I am trying to do some Newton's method-type stuff in Mathematica. I want to build a While loop that does the following: - Take input r. - Compute some quantity f(r). - Update the value of r to f(r). - Repeat until |g(r)| < C for some fixed constant C. The third (boldfaced) step is...

I am using Mathematica to create a formula to solve for (Vs) in an equation shown at the top of the attached image. Using the assumptions shown, Mathematica outputs three possible solutions, all of which appear to be incorrect when I check them using actual values. I get this error when...

On mathematica: Solve the differential equation d^2 x(t)/dt^2 + x(t)(x^2(t) − 1) + t = 0 numerically, subject to the initial conditions that x(0) = 1 and dx(0)/dt = 0. Use Plot to plot the solution for the domain t 2 [0, 10]. 2. Above is what I'm trying to do. Below is what I've...

I've got a Mathematica question which might be quite basic, but I couldn't find much about it in the documentation (possibly because it's so basic) so please bear with me! I have a set of data, call it xi(ρ), which I want to integrate over some distribution function (log-normal in this case)...

Hello, I'm quite new to Mathematica and stuck at a point, where I have searched for hours to find a solution, but there seems no way out. Let's say we have two functions, f1[x_,y_]=x+y f2[x_,y_]=x*y How can a build a function f3, which is e.g. the sum of the other functions f1 and f2...

Hi dear All Sorry for a stupid question, but I am really newbe in M. I have some function, for example D[y[r],r]. Now I want to substitute y[r] to Sin[r] and to ask Mathematicato make all the calculations. (i.e I want to get Cos[x]) If I make smth like D[y[r],r]/.y[r]->Sin[r] or D[y[r], r]...

Hi, I wish to listplot a list object against a scale that is NOT the component number of the vector, but is actually a well defined function of the component number, and I am lost how to do this? changing "Ticks" didn't help, or I did it wrong, so I am wondering if anyone knows how to do this...

Hello all :) I'm just beginning trying to use compiled version of several simple functions. And right at the beginning, I stumble onto a “Numerical error” error message which puzzle me… Here is my simple code : 11/18/11 12:51:07 In[18]:= \[Epsilon]IntrinsicSiliciumC =...

hi i want to sum over two indices i and j . the elemet that i must sum is (x^(i,j))-i that is x has superscript i,j and subscript i. but in mathematica it gives me error. here is the notebook : http://www.mediafire.com/?novtz7t0liu9u78 thanks (:

Homework Statement I have list( Depth vs. Deflection) of data which requires plotting with the polynomial degree of 14. Homework Equations I need help to figure out how to plot with polynomial degree. The Attempt at a Solution

Hi, guys. I need to control Mathematica through the MS-DOS command line in Visual Basic for Applications as part of a macro for CST Microwave Studio. I can call Mathematica through the command line just fine with Shell("math", vbNormalFocus) but when I try to enter commands afterward...

Hi there. I have a problem with this. I'm trying to plot a polynomial fit done with origin 8.5 on mathematica. The thing is that the polynomial plot I get in mathematica from the coefficients given in originlab don't match, and I don't know why. I'll let you some pics of what I'm trying to do...

Hi. In Mathematica I have tensor T for example In[]:=Dimensions[T] Out[]:={3,3,4} now i have index of some element in the List form index={1,2,3} Now I want to use the element whose index is in variable index. How can I do it?

hi i solve numerically two coupled equation and obtain two function x[t] and y[t]. how i plot x[t] versus y[t] so that horizontal axis to be x[t] and vertical axis to be y[t]. here is the notebook of mathematica http://www.mediafire.com/?g4sa3zi630vi8nl thanks

Hello!: I want to know if it's possible to use the Collect command in a function. For example, I have this code: Subscript[E, 1] = \!\( \*SubscriptBox[\(\[PartialD]\), SubscriptBox[\(\[Omega]\), \(1\)]] \*SubscriptBox[\(\[Pi]\), \(m1\)]\); Subscript[E, 2] = \!\(...

The questions arises because I want to use the solution of one PDE as initial condition to solve another. Then using NDSolve, the first solution is given by InterpolatingFunction. I tried, it takes the whole afternoon, almost kills my computer but still not giving any result. Another computer...

Hello everyone, I copy-paste here a little bit of code: In[4417]:= x = (1.5` + 0.` I); y = (0.` + 0.` I); (* 1 *) ArcTan[x, y] (* 2 *) ArcTan[x // Chop, y // Chop] (* 3 *) -I Log[(x + I y)/Sqrt[x^2 + y^2]] {y == 0, Re[y] == 0, Im[y] == 0, Im[x] == 0} Out[4419]= -1.5708 + 0. I...

THIS ISN'T WORKING AT ALL! I'm trying to define a matrix M in terms of a predefined matrix N by using the following for loop: For[a=1,a<=12,a++,M[[a,a]]=N[[1,a]]] So I just want the diagonal of M to be the first row of N. But this is not working at ALL. Does anyone see what I'm doing wrong?

Dear all, I have difficulty to solve this code which involves looping, In [1] := m = 1; n = 1 ; A = -1 ; B = 5 ; In [2] := m = 1; n = 3 ; A = 8 ; B = -2 ; In [3] := m = 1; n = 5 ; A = 9 ; B = 7 ; In [4] := m = 3; n = 1 ; A = -2 ; B = 8 ; In [5] := m = 3; n = 3 ; A = 4 ; B = 3 ; In...

I am solving a PDE using NDSolve. It always give a message like: "For the method`IDA, only machine real code is available. Unable to continue with complex values or beyond floating-point exceptions." What does this mean? My code is as following. NDSolve[{∂t S[z, t] == -I z S[z,t] -I...

How can a system of non-linear differential equations be solved using Mathematica? More specifically, I understand the process that needs to be executed, but I don't understand how to make it work syntactically. The process as I understand it: Four expressions are given in four...

About serval differential equations where A, B, D, g, \chi, c are functions of r \begin{eqnarray} &-\frac{{\chi}'}{r}+\frac{c'}{c}\left(\frac{g'}{g} -{\chi}'\right)=\frac{e^{\chi}(q A B)^2}{r^2 g^2 c^2}& \\ &c c''+c c'\left(\frac{g'}{g}+\frac{2}{r} -\frac{{\chi}'}{2} \right)=-\frac{B'^2}{2...

Hi Im doing a 2 dimensional heat spreading simulation. I've created a matrix with 3 indices with the first index being for time step and the two other for element coordinates. height = 20; width = 4; a = 0.5; J = Round[height/a]; L = Round[width/a]; h = 0.1; roomT = 20; T = 90...

Greetings, I have a nagging issue that keeps annoying me in Mathematica. If a Mathematica function outputs a number I want in the form "variable→number", is there a function I could use or something simple I could type to get the number itself, rather than in the Root[variable, number]...