2
votes
2answers
16 views

How to simplify a differential equation?

Now I get a differential equation like this: (-1 + x) (1 + x)^2 == (2 (1 + x^2) (1 + x^4))/(-2 x (1 + x + x F[x]) + (-1 + x^3) F'[x]) I want to get the standard ...
1
vote
1answer
5 views

Faking MoleculePlot for compounds where it isn't available

Mathematica's ChemicalData has a lot of useful information, but many compounds only have flat 2D structure diagrams rather than the cool 3D ...
0
votes
0answers
12 views
0
votes
2answers
19 views

Mathematica Integration Problem

I am new user of Mathematica. Can anybody help me to solve this integration? I really needs your help. Integrate[(1 - (1/(1 + A x^(-ao)))) x, {x, 0, r}] Can ...
0
votes
0answers
13 views

How can I bypass the limitations of init.m?

In a series of QA it has been pointed out that init.m suffers of heavy limitations (see as example, Automatically load packages at startup or Why can't I import ...
1
vote
3answers
43 views

Get the coefficient matrix from a quadratic form

Suppose I have a quadratic form of qf = a x^2 + b y^2 + c z^2 + 2 d x y + 2 e x z + 2 f y z How can I easily to get the symmetric matrix A, such that ...
1
vote
3answers
83 views
0
votes
0answers
15 views

Change position of data labels in BarChart3D

What would be the easiest way to manipulate the position of the chart labels in "Grid" layout in a BarChart3D? For example: ...
0
votes
0answers
31 views

Replace every power of $e^{i\theta}$ with $z$ [on hold]

If I have the expression $\frac{1}{13-\frac{5}{2} i \left(e^{-i \theta }-e^{i \theta }\right)}$ and I want to replace each $e^{i\theta}$ with $z$, so that the result is ...
-1
votes
0answers
44 views

How to find a root for an integral equation?

I try to find numerical solution $E_f$ to satisfy the following equation: ...
2
votes
1answer
82 views

Syntax f[x_][y_]

Need to understand the principe of the distinction between f[x_,y_] and f[x_][y_] It seems also that ...
5
votes
1answer
107 views

Evaluating standard functions of general quaternions symbolically

Mathematica can easily compute exponentials and logarithms of concrete quaternions: ...
1
vote
1answer
64 views

Finding roots of Bessel function $y=3J_1(x)+xJ_1'(x)$ is returning inaccurate roots. Not Kernel bug [on hold]

I can't figure out why Mathematica is returning the incorrect roots. The first five should be 2.9496,5.84113,8.87273,11,9561, and 15.0624 according to my textbook. ...
0
votes
0answers
63 views

Root of a cubic is not always real [on hold]

In my Mathematica output, the following root object occurs ...
10
votes
1answer
83 views

Is it better to completely forget about the existence of PowersRepresentations?

I noticed that in several cases the performance of PowersRepresentations is hugely worse than that of IntegerPartitions. (Mma ...
9
votes
2answers
168 views

Is it possible to get the (x, y) position of nodes in a `Graph`?

Given a graph... RandomGraph[{20,40}] ...is it possible to retrieve the (x, y) coordinates at which the nodes are drawn? ...
0
votes
0answers
29 views

Plotting function described by other functions!

I want to plot and manipulate my VS function which comes from the other functions above it. So, what should I use in order to draw my function considering that it is described by other functions. I ...
8
votes
3answers
219 views

Deriving a PDF for an annulus distribution

I would like to derive the PDF for an ''annulus'' type distribution, defined by the parameters $\theta\sim U(0,2 \pi)$ and $d\sim N(0,\sigma)$; where $\theta$ is the angle round a circle of radius ...
5
votes
0answers
41 views

Bug in Mathematica 9 (Quaternion)

The code: << Quaternions`; Exp[Quaternion[1, 0, 0, 0]] produces an error: ...
3
votes
0answers
118 views

Integrate producing bad result

I noticed a bug in Mathematica. It computes incorrectly a definite integral ...
0
votes
0answers
33 views

A function for replacment in mathematica [closed]

when you have too many replacements such as a1 x+ b2y + c1 z/.{a1->s^2+b^2,b1->r^2+g^2,c1->f^2+k^2} is it possible to define a vector like this ...
2
votes
2answers
59 views

How to find intersection points of linear and semi-logarithmic plots

Hopefully the title depicts what I am trying to do. Below is a figure of my calculations that is shown in logarithmic scale in the x-axis. I am trying to find a way to find the intersection point at ...
1
vote
1answer
41 views

A question on JordanDecomposition in Mathematica

How can I have Mathematica show me also the inverse matrix of the similarity matrix of JordanDecomposition of a matrix? Obviously I need to use here the ...
0
votes
1answer
53 views

Loading FeynCalc

I am trying to install the FeynCalc package, but I cannot load it, it always gives the following errors: Loading FeynCalc from /home/gabi/.Mathematica/Applications SetDirectory::cdir: Cannot set ...
1
vote
3answers
58 views

expressing a rising factorial as a polynomial

I have an equation in $x$ as follows: $f(x)=\prod_{j=0}^{k}(j+x)=x.(1+x).(2+x)\cdots.(k+x)$ I want to express this as a polynomial in $x$, i.e., as $a_0x^0+a_1x^1+\cdots+a_kx^k$ I tried doing the ...
3
votes
2answers
136 views
10
votes
1answer
127 views

Why FoldList 5 times faster than Apply for matrix multiplication?

Consider this list of $2\times 2$ matrices: list=RandomReal[{-2,2},{500,2,2}]; Now compare timings of Apply and ...
0
votes
0answers
44 views

What is it with MemberQ? [closed]

Look at this operation MemberQ[x^3, x^3] (* False *) Is it correct, or a bug?
7
votes
2answers
275 views

How to measure the slit size from given image using mathematica?

I want to measure the size of the optical slit from the microscope image. Here is the image. The dimension of image data is {1300,1030} and the real pixel size is 6.7 micron. But the problem is ...
13
votes
2answers
301 views

upper envelope of data

Here is a ListPlot[] of some data. Clearly, there is a fairly smooth upper envelope - the question is whether there is an nice way of extracting it...
0
votes
1answer
37 views

NDSolve with coupled ODE's and unknown singularities

I have two coupled ODEs that I am trying to solve numerically. It appears that there is a singularity in the solution to the equations which I am unsure how to get past. Both functions $\alpha$ and ...
0
votes
0answers
28 views

Check if interpolated function passes through a specified region

Is there an efficient way to check if a curve that was obtained as an Interpolating Function (from solving differential equations numerically) passes through a given region? I am solving for two ...
3
votes
1answer
52 views

Pareto optimal fronts using internal function?

Reading this question: How do I estimate the Pareto front in my multiobjective optimization problem? I found @Daniel Lichtbau's interesting answer. Yet I don't know how such an "internal function" ...
2
votes
1answer
43 views

Solving a big number of non linear equations

I have three trapezoids. The first sharing its upper side (I will call b_{i+1} in the code) with the second, the third sharing its lower side with the upper side of the second. All shared sides are ...
1
vote
0answers
12 views

Palette Sizing Options

I am writing a palette to work with units on Mathematica 9, using just PasteButtons, and have a Button map that works as I want it to, but the formatting of the palette itself is giving me issues. I ...
1
vote
2answers
58 views

ListPlot with colors

Let's create some sample data n = 100; d00 = Table[{RandomReal[{-1, 1}], RandomReal[{-4, 4}], RandomReal[{-1, 1}]}, {i, 1, n}]; Now I want the following: create ...
0
votes
0answers
49 views

Trying to create a model and manipulate plot

I have been trying to learn mathematica to implement financial models in it. However, I am still very inexperienced in this :) Currently, I have what is presented below but I can't figure out why it ...
2
votes
1answer
144 views

solving coupled differential equations with parameters subject to optimization problem

I have an equation, but I don’t know how to program it in Mathematica: x[0]==1; y[0]==1; x'[t]==(a+b) x[t] y[t]; y'[t]==a b y[t]/x[t]; where ...
2
votes
2answers
60 views

Solve transfer function with non-zero initial conditions

Hand computation I have a transfer function defined as $\frac{0.6p+1}{0.6p^2+2.2p+8}$ which was derived from a circuit. Solving this by hand gives the equation, $$i(t)=Ce^{-1.83t}\cos(3.16t + \phi)$$ ...
0
votes
0answers
28 views

How to speed up Solve command in Mathematica 8.0?

I have two complicated mathematical functions $f(s)$ and $g(M)$ that are complicated functions of $s$ and $M$ respectively. I would like to solve the equation $f(s)=g(M)$ in order to plot $s$ vs. $M$. ...
2
votes
0answers
32 views

ColorBars or PlotLegends for ElementMeshSurfacePlot3D

I want to produce a colorbar legend to the output from ElementMeshSurfacePlot3D (Mathematica 10). The pde was solved using NDSolveValue (FEM pdesolution is the resulting interpolating function) over a ...
1
vote
0answers
59 views

Distinguish hashtag # operator when using multiple functions

I would like to do this list = Append[list[[#]],Map[list2[[1, #]] & , list[[#, 4]], {2}]] & /@ Range[Length[list]]; But I would like to substitute ...
2
votes
2answers
56 views

Integral invoving product of Whittaker functions

I'm trying to evaluate the integral $$ \int W_{0,a}(x)\,W_{1,b}(x)\,\frac{dx}{x}, $$ where $W$ denotes the Whittaker $W$ function, and $a,b\in[0,1/2]$. Using the Whittaker differential equations that ...
4
votes
1answer
425 views

webMathematica interface for Mobile apps

I was reading about webmathematica but it has mentioned that it is for websites and mobile apps depend on wolfram alpha to get its work done. But since exact mathematica code doesn't work in alpha, it ...
10
votes
2answers
574 views

Difference between = and Ctrl + =

What is a difference between $\textbf{=}$, and Ctrl + $\textbf{=}$? For instance there are some examples, but result is same. and
5
votes
1answer
252 views

How to construct a tree from a notebook?

Given the notebook itself we can think of it as a tree graph: the root vertex is the empty notebook itself, the headers of cell groups are vertices, and all other cells as leaf vertices. I'd like to ...
0
votes
1answer
30 views

Export list entries under a certain condition without using loops

I have a big list that contains many 3D- chains (set of points) and for each of them a polynomial. So the structure of my list is for example ...
-1
votes
0answers
72 views

Rudimentary/basic simplifications of expressions not carried out--very puzzling!

Here's the raw input cell form--trying to follow MarcoB's suggestion--of the "offending" expression "g2": g2 = Piecewise[ {{(1/(1435*ra))(2(-1 + ra)^6*(11*ra^3*(-896*(201 + 16*rb) + .10*(368699 ...

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