What is Mathematica: Definition and 1000 Discussions

Wolfram Mathematica is a software system with built-in libraries for several areas of technical computing that allow symbolic computation, manipulating matrices, plotting functions and various types of data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other programming languages. It was conceived by Stephen Wolfram and is developed by Wolfram Research of Champaign, Illinois. The Wolfram Language is the programming language used in Mathematica.

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  1. Hepth

    Mathematica Mathematica : Numerical Integration

    So I have to numerically integrate a function that is quite difficult. I could post it, but its long. Regardless, there are 5 variables I am integrating over. The first is independent. The next 4 are subsequently dependent on the integration limits of the previous. Not a big deal. something...
  2. R

    Change variables and expand around new variable (Mathematica)

    I have a differential expression that I want to expand to some order around infinity (it's for calculating weak-field limits in GR). I have two functions, B(r) and n(r), and some expression involving them along the lines of n[r] (3 r B'[r]^2 - 4 B[r] (2 B'[r] + r B''[r])) Basically I want...
  3. F

    Mathematica Mathematica remote kernel hangs after password

    Hey all, I'm trying to setup remote kernels via ssh to run numerics on my cluster via my laptop. So far I've managed to get the laptop MM front end to connect via ssh to the cluster, but then it just hangs on the evaluation (after password entry). In the kernel config options I told it to...
  4. J

    Top Free Mathematica Packages for Calculating GR Tensors and Derivatives

    Hi, I am interested in obtaining a FREE mathematica package that can: 1) Calculate standard GR tensors (connections, Ricci, Einstein etc.) 2) take covariant derivatives 3) and define tensors Does anyone know of a good Mathematica package?
  5. A

    Mathematica Mathematica: Why isn't this command with Assuming working?

    Mathematica: Why isn't this command with "Assuming" working? I'm trying to execute the following command: Assuming[g >= 0 && t >= 0, Refine[Abs[1 + I g t ]]] I expect it to spit out \sqrt{1+t^2g^2}, but instead I'm just getting \text{Abs}[1 + i g t], which is obviously pretty...
  6. G

    Mathematica Mathematica, Table Generation & Rescaling Axes

    Hi, Have a problem: I'm generating 2 lists in Mathematica: In: time = Table[(r - 1.0)/10.0 , {r, 10}] Out: {0., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9} In: noise = Table[RandomVariate[NormalDistribution[0, 1.4], 10]] Out: {2.16764, -1.38203, -0.395928, -0.58616...
  7. J

    Mathematica Mathematica: Problem Computing Fisher Information of pdf

    Hello, I'm trying to calculate Fisher information (and eventually the Cramer-Rao lower bound) for this particular pdf with Mathematica: \text{pte}[t,\Theta ] = \frac{P_{\text{ec}}}{\tau _d-\tau _r}\left[e^{\frac{-(t-\Theta )}{\tau _d}}-e^{\frac{-(t-\Theta )}{\tau _r}}\right]...
  8. parazit

    Mathematica How To create an .exe file from Mathematica ?

    How To create an .exe file from Mathematica code ? Hi, I just wonder is there a way to create an exe file from a Mathematica code, that runs just with double-clicks on it ? When it starts running it may ask some values for some variables and when one of them entered the others and the...
  9. P

    Mathematica Mathematica, gradient plot on the graph

    Hi, I need to plot a vector field 2x,2y,0 which is the gradient of the function x^2+y^2. I need to plot it only in some interesting points (points on the paraboloid x^2+y^2). So I tried something like a=Table[{{x,y,x^2+y^2},{2x,2y,0}},{x,-2,2,0.5},{y,-2,2,0.5}] ListVectorPlot3D[a] It...
  10. G

    Mathematica [Mathematica] Solving Heat Equation in Spherical Coordinates

    Hello Folks, I have this equation to solve (expressed in LaTeX): \frac{\partial{h}}{\partial t} = \frac{1}{n} \left[ \frac{1}{r^2 \sin^2{\phi}} \frac{\partial}{\partial \theta} \left( K \frac{\partial h}{\partial \theta} \right) + \frac{1}{r^2 \sin \phi} \frac{\partial}{\partial \phi}...
  11. I

    Mathematica Mathematica does not completely evaluate expressions.

    I've defined A and B to be two affine transformations on \mathbb{R}^2. Then, I defined C and D to be some kinds of compositions of A and B, for example: C = Composition[A,B,B,A,A][{x,y}] D = Composition[B,A,B,A,B][{x,y}] Now, I want to evaluate expressions like: X =...
  12. R

    Mathematica Taylor Expansion in Mathematica (Multivariate)

    Hi! I'm trying to linearize a function f which is dependent of 4 variables, each one dependent of time. f[var1_,var2_,var3_,var4_]:= ... expression I use Series[f, {var1,var10 ,1},{var2,var20 ,1},...] syntax as I read on the documentation center. The problem is that the program...
  13. I

    Mathematica Composition of Vector Functions in Mathematica

    I want to define something like: A\left(\begin{matrix} x \\ y\end{matrix}\right) = \left(\begin{matrix} 1 & -1 \\ -1 & 1 \end{matrix}\right)\left(\begin{matrix} x \\ y\end{matrix}\right) B\left(\begin{matrix} x \\ y\end{matrix}\right) = \left(\begin{matrix} 0 & 1 \\ 2 & -1...
  14. S

    Mathematica Plot of vector valued function in mathematica

    Hi,I have vector valued function u=(u1(x,y,z),u2(x,y,z),u3(x,y,z)) and I want to plot this function in mathematica.how can I do this? I used Plot3D command but this doesn't look correct.
  15. N

    Mathematica How to Ignore Excel Headers in Mathematica for Statistical Analysis?

    Excel Headers --> Mathematica I have a large Excel .xls file. Miniature version shown below: Test1 Test2 75 64 58 85 81 55 64 63 70 94 88 90 78 96 96 98 54 97 75 61 I would like to do some statistical...
  16. N

    Mathematica Mathematica: Evaluating integral numerically

    Hi I am trying to evaluate an integral in Mathematica numerically as I have done many times before, but it simply won't work. To make things easy on everybody, I have attached a notebook with the integral. I simply can't see what is wrong here. I'd be happy to receive some help. Niles.
  17. N

    Mathematica Data format AFTER import into Mathematica from Excel.xls worksheet

    . I have a large Excel worksheet (200 columns, 4,000 rows). Every column has a unique and carefully chosen title/label. I'm attempting to use it within Mathematica to create a large number of contour plots (1,000) -- using three columns at a time, for x, y, z. The import, I suppose...
  18. N

    Mathematica Mathematica: Evaluating integral

    Hi I need some assistance with the attached integral. I have tried performing it in Mathematica, but it doesn't give me the result in closed form. It just shows the integral. I have attached my notebook if someone wants to test it out. I would be very happy to receive some feedback as I...
  19. B

    Mathematica How can I fix the sign issue in my NDSolve command in Mathematica?

    Hi, I'm trying to model a process by making mass and energy balances using the NDSolve. It reaches the maximum number of steps It is working when I put "-" sign in front of this [Rho]p*(1 - ec)*\[CapitalDelta]H*D[q[z, t], t] (in 3rd equation) in the NDSolve command. But it should be "+"...
  20. M

    Mathematica Generating random numbers with Mathematica

    Hi everyone, I am trying to generate 200 random numbers from an exponential distribution which have to add to one. I guess I need a loop where in each step I generate a random number from the exponential distribution and check the sum, if it is less than one I add the number to a list and if...
  21. R

    Mathematica Analyzing a text file in mathematica

    hi, I have a big text file which includes lots of text and data (gaussian log file (it's a scan file)) and I need to extract some data from it. so I need mathematica to search along the textual data and find some strings and put the value in front of that string into a variable. can you...
  22. Z

    Dynamical System Analysis using Mathematica

    Hello there, Let me start from the beginning. I have dynamical system described by two autonomous ODEs (eqn1, eqn2). To find equilibrium points I used NSolve[{eqn1 == 0, eqn2 == 0}, {x, y}] which gave me 5 solutions in a form {{x->2, y->0},{...},...}. I also constructed Jacobian matrix using...
  23. S

    Integration result varying in mathematica 5.2

    indefinite integral of Log[x] comes out to be -x + x Log[x] but, the general solution should be x ln(x)+C Such things also occur when using DSolve command to solve differential equations. Please help!
  24. I

    Mathematica Mathematica- adjusting FrameTicks option

    Hi I want to plot the data in Mathematica data={{0.608, 0.05}, {0.43, 0.1}, {0.304, 0.2}, {0.248, 0.3}, {0.215, 0.4}, {0.192, 0.5}} I am trying to use ListLinePlot. The problem does not say to use any particular command. But I chose ListLinePlot... Here is the code I am using...
  25. M

    Mathematica Mathematica: Problem with For loop increments

    I'm having a recurring problem in mathematica when I try and introduce a simple for loop. For instance, I have the code shown below. It should increment my var value, and calculate a value of 'initial' for each 'var' value. These should then be recorded under the name RMPvalue[var] so I can...
  26. N

    Mathematica Mathematica: Extracting histogram information

    Hi I have a histogram of some numbers following a PDF, such as Histogram[RandomReal[1, 100]] What I want is to extract the information contained in this histogram in a list, i.e. get a list of the bin value (e.g. the average value it represents) and the number of entries in it. Is using...
  27. D

    Mathematica LaTeX in Mathematica Slideshow

    I am trying to put together some short slideshows in Mathematica for educational purposes. I'm using Mathematica in Slideshow mode so that it will be a nice looking presentation that also has embedded graphs etc. I thought this would be easy since Mathematica exports LaTeX and imports full LaTeX...
  28. I

    Mathematica Mathematica plotting several functions

    Hi I need to plot \sin(x) and its first,third, fifth power series expansion on the same plot. here's what I did T[n_,x_]:=Normal[Series[Sin[x], {x, 0, n}]] Plot[{Sin[x], T[1, x], T[3, x], T[5, x]}, {x, -2, 2}] But I got following errors. General::ivar: -1.99992 is not a valid...
  29. I

    Mathematica problem involving integral

    Hi We know that in Debye theory, C_v=9kN\left(\frac{T}{\theta}\right)^3 \int_0^{\theta/T} \frac{x^4 e^x}{(e^x-1)^2}\;dx is the heat capacity of the solid. I want to plot C_v/3Nk as a function of T/ \theta from 0.001 to 1.4 using mathematica. The hint says to use NIntegrate. Now...
  30. J

    Mathematica Deleting Duplicate Values Of Matrix In Mathematica?

    Hey guys, I have a x row by 3 column matrix (its big and the amount of rows varies). I want to... ...Keep ONLY pairs of rows with the same value in their first column and delete the rest. Meaning if a row has a unique first column value or if three rows have the same value in their...
  31. G

    Mathematica Troubleshooting Mathematica Eigen Problem: Analytical vs. Numerical Results"

    Hi! I'm having some trouble with this. In the code I define two matrices, then calculate its eigenvalues/eigenvectors, and finally I plot the absolute values of the components of the eigenvectors. The results are consistent with (I'm quite sure) the analytical ones but only below "t approx 30"...
  32. E

    Mathematica Simple Parallelization with Mathematica

    I have a program with Mathematica and I would like to run it in parallel. The essential of the code is actually run a lot of cases, changing some parameters. In other words, it means that each case is totally independent of the other. But I'm not quite sure about how to do it. To exemplify...
  33. J

    Mathematica Mathematica: Printing Numeric Result

    Hey, So I am fairly new to Mathematica (and the physics forums too). I am having a problem with mathematica not calculating the numeric result to an very complex integral. My question is, how do I force it to evaluate the integral as a number? I'm assuming that the integral of a square root...
  34. K

    How can I plot b[a]/b[0.0001] vs. a using Mathematica?

    hey guys, I came across a research paper stating to numerically integrate the following equation. 2/3 a^2 b''[a] + (1 - w[a]) a b'[a] - (1 + w[a]) (1 - 3 c w[a]) b[a] A Boundary condition is given b'[0.0001]=0 Where; w[a_] := 2*a^(3*(1 + c))/(1 + 2*a^(3*(1 + c))); (c=1) (c is a...
  35. N

    Mathematica Printing results if certain conditions are met in Mathematica

    Hello everyone, I have for loop in Mathematica. After every step Mathematica has new results calculated. I want to see only some results, those who met certain conditions, not results from all steps. Say, I have 10000 steps and I don't need all 10000 results, but only those that met certain...
  36. I

    Mathematica Parallel calculations in Mathematica

    Hello PF. I wanted to optimize time expenditure on some calculation that I'm doing. A natural way to do this can be by computing parts in parallel. Now when I say "parts" I don't mean that some computations are wholly independent of other computations. My situation is that I have a bunch of...
  37. K

    Mathematica Mathematica: How to export notebook to MS word

    Hi everyone, Iam just wondering how to export the mathematica nb. file to MS word? Preferably word 2003 version. I have tried to use cut and paste method into word, however, the presentation in word does not look nice. Any advice is very much appreciated.
  38. M

    Mathematica Find all roots of an interpolating function in Mathematica

    Hi, I've got an interpolating function which has been generated from using NDSolve and I'm trying to find all the values of x for which the y value is equal to 2. I've constructed a (much) easier example to show what I mean. Suppose I have a set of points which I have generated an...
  39. N

    Mathematica Mathematica: Convolution between Lorentzian and Gaussian

    Hi I have the following code: lorentz[A_, Ox_, Oy_, FWHM_, x_] := A (1/3.14) FWHM/((x - Ox)^2 + FWHM^2) + Oy; gauss[A_, Ox_, Oy_, x_, C_] := A Exp[-(x - Ox)^2 C] + Oy; Convolve[lorentz[1, 0, 0, 1, x], gauss[1, 0, 0, x, 1], x, y] It takes extremely long time for this to finish -- is it...
  40. S

    Mathematica Mathematica: mean of 2d function

    Dear all, I wonder if there is a function implemented in Mathematica to find the average value of a 2d function f(x,y). So averaged over a specified domain. Thanks in advance for any help! Sue
  41. K

    Mathematica Mathematica: Need help to modify the code

    Hi all, I need help to edit the code so that the arrangment of the outputs match the one that Iam looking for. For instance: term[n_Integer, m_Integer] := Apply[Dot, Table[matg[[i]], {i, m + 1, n}]].hl[[m]] /; (n >= m); Subscript[lay, s_] := Sum[term[s, i], {i, s}]; In[1]...
  42. L

    How Can I Define Tags Within My Code Using Sow/Reap in Mathematica?

    I am trying to use Sow/Reap in Mathematica to replace Append in my code. The problem is that I need to define the tags within my code, but doing so doesn't reap the desired results. A simplified version of my code is Clear[tag]; Reap[tag = {a,b}; Sow[1, a];Sow[2,b];, tag] However, if I...
  43. N

    Mathematica Construct matrix from vectors in Mathematica

    I have defined vectors which are to be column vectors of some matrix. How to tell Mathematica to construct such matrix whose column vectors are already defined vectors?
  44. K

    Mathematica plot question, dsolve

    Hey guys, I'm using Mathematica to plot some graphs and I'm having a bit of a hard time. First I have to solve the following equation, 2/3 a^2 b''[a] + (1 - w[a]) a b'[a] - (1 + w[a]) (1 - 3 c w[a]) b[a] Boundary condition b'[0.0001]=0 Where; w[a_] := 2*a^(3*(1 + c))/(1 +...
  45. K

    Mathematica plot question, dsolve

    Hey guys, I'm using Mathematica to plot some graphs and I'm having a bit of a hard time. First I have to solve the following equation, 2/3 a^2 b''[a] + (1 - w[a]) a b'[a] - (1 + w[a]) (1 - 3 c w[a]) b[a] Boundary condition b'[0.0001]=0 Where; w[a_] := 2*a^(3*(1 + c))/(1 +...
  46. E

    Mathematica Streamlining Replace in Mathematica 8

    Hi guys, i have expressions of the type (X*a)(X*b). I want replace this by X^2(a*b). So i tried building a block which does nothing but %//.(X*a_)(X*b_)->X^2(a*b). However, this works only if a is distinct from b. If a and b are equal if HAVE to use the replacement command...
  47. S

    Mathematica W. Mathematica 8 stays running and does not evaluate

    Hi I am a user of Mathematica as a tool for calculation in Structural Mechanics. I had a problem recently in the integration of expressions a bit long, and honestly I do not understand what might be causing the slowdown. I want to just evaluate this: This is for the Raileygh-Ritz...
  48. S

    Mathematica Mathematica array plot won't plot and it erases all of my stored variables

    Hi, I wrote some code on a computer at school. dim = 50; Ediff = ConstantArray[0, {dim, dim}]; \[Lambda] = .5; steps = 10; Ediff = ConstantArray[0, {dim, dim}]; L = 1; For[xs = 1, xs <= dim, xs++, For[ys = 1, ys <= dim, ys++, Ediff[[xs, ys]] = Ediff[[xs, ys]] +...
  49. R

    Converting Standard For Loop to Mathematica Code for 2D Iteration?

    here is the pseudo java (processing) code I'm trying to run float x0,y0,x,y,t; x0 = 2; //arbitrary value y0 = 5; //arbitrary value x = x0; y = y0; for(int t = 1; t <= 100; t++){ //one hundred iterations t =atan2(y,x); x += cos(t); y += sin(t); print( x...
  50. S

    Mathematica View open windows in Mathematica

    Is there a way to bring up all of the notebook you're currently working with in Mathematica? Sometimes, a notebook I'm using disappears and I can't call it back up.
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