# All Questions

59,223 questions
65 views

### Indexed function recursion problem

I am trying to use indexed functions in a For loop; to illustrate, I give a trivial example. f[1, x_] := x^2 Now, I can define: ...
51 views

32 views

### Unable to import an .eps file

I am trying to import an .eps file into Mathematica, but I am getting an error. I tried this ...
95 views

### Concerning the origin of four terms in DSolve's hyperbolic solution to an ODE

Typing DSolve[{g''[y] - k^2/Gy g[y] == 0}, g[y], y] where $k$ and $G_y$ are constants gives \left\{\left\{g(y)\to C_1 \exp\left(\frac{k y}{\sqrt{G_y}}\right)+...
44 views

### Solving a PDE solved by the method of lines giving a warning about bad local spatial error estimate

I use the method of lines to solve the PDE ...
53 views

### Help in advection-dispersion equation using NDSolveValue

i have the advection-dispersion equation: Dz*D[u[z, t], z, z] - as*D[u[z, t], z] == D[u[z, t], t] In which Dz and as are constants equals to 0.0000738739 and 2....
32 views

I'm trying to moving up the square signal to positive values. First, I'm amplifying a sine wave then converting it to a square signal, but when I use an amplifier adding a dc signal to the square, ...
195 views

### Simulate the appearance of a plane illuminated by a nearby point source

I'd like to simulate the appearance of a diffusely reflecting plane surface illuminated by a nearby point source. ...
118 views

### Direct and easy calculation of the N-th derivative of a function at 0?

Does Mathematica have an easy way to calculate the n-th derivative of a function at zero? I was looking for something along the way D[e^x,{x,n,0}]. How do I do ...
37 views

### Difficulty in Animation of Inverted Pendulum from Interpolating Function

I was trying to model an inverted pendulum system and control it. I successfully got the plot but I'm not able to use the data to animate a graphically created inverted pendulum. Run the code serially,...
42 views

### Using constraints when solving a trigometric equation

I'm trying to learn how to add constraints/assumptions to equations when using Solve, sp as to avoid multi-valued solutions. For example, I'm trying to use ...
73 views

### Why does Mathematica not integrate my function? [on hold]

Why doesn't Mathematica integrate my function? Srry I am at the first time at this forum. So i have no idea how it works. I hope the following input is enough. ...
45 views

### Mathematica symbolic question - Subexpressions?

Apologies in advance if this has been asked but I cannot find any information. I'm calculating the determinant of a large symbolic polynomial matrix. In the result are symbols such as this: as in ...
68 views

### Producing MoleculePlots of pigments

Of course no chemical database is complete, but I would like to create as large a list of MoleculePlots of pigments (organic or inorganic) as is available through ...
189 views

### Geography in 3D perspective

I would like to build a GeoGraphics map showing a z-elevated perspective (e.g. the view from a plane). Specifically, I'm looking to use multiple ...
44 views

### Part::pkspec1: The expression j cannot be used as a part specification

I want to do some stuff with symbolic arrays like this a[[j]] + a[[j + 1]] == a[[j - 1]] + a[[j - 2]] But upon declaring such an expression I get ...
41 views

### Can a logarithm function with two variable be expressed as a Meijer-G function? [migrated]

Let {x},{y}>0 and {a},{b}>0. can the function log(1+ax+by) be expressed as a Meijer-G function?
53 views

### How to extract the data points in tabular form from a 3D region plot

I want to solve an inequality e.g. RegionPlot3D[x^2 + y^2 + z^2 > 300, {x, 2, 9}, {y, 3, 10}, {z, 4, 12}] and store x, y, z...
33 views

### What is causing this error in the Interpolation function?

I am using trying to understand someone else's code in Mathematica for the Finite Difference Method, except I changed a few values, but none of the code itself. Everything except for the Interpolation ...
23 views

### Why is an integration error appearing during this code?

I'm really confused about this to be honest. If i evaluate approx[x,k] for some k, and then input the list into the Plot function, I get a plot. But if I try to use approx[x,k] directly, I get an ...
28 views

### How to save data and show step sizes when using components and data structures of NDSolve?

In some applications, it is advantageous to access components of NDSolve. However, we could also need to observe the step size taken in the numerical integration, ...
27 views

### Analytic solution of a system of six ODEs [duplicate]

I have a system of six ODEs for six function. I want to get the analytic solution of the system. I have used DSolve, but it can not solve it. The code is: ...
20 views

### Acquire a single-variable function by slicing a 3d graph along a given line

Consider my Calculus 2 math problem: Given a function f[x,y]=x^2-3xy and two vectors a = {1,2} and b = {1,1}. Spanning a linear ...
115 views

### Who or what is named character Andy?

I suspect \[Andy] meant to represent a staff member, or at least a person of importance. I tried the F1-"Wolfram Search", Wolfram|Alpha and a simple Mma.SE & ...
84 views

### Changing Color of error messages

I would like to change (from the stylesheet) the colors of the error messages. For example, trying to evaluate Solve[wrongsyntax = 0, var] gives an obvious error ...
410 views

### How to generate binary array whose elements with values 1 are randomly drawn

I am trying to generate a binary matrix (whose elements are 0 or 1) of dimension 20x20. To do this, I want to supply as input the number of matrix elements that will take value 1. After, I want to ...
52 views

### How to solve this equation numerically? [on hold]

Two Gaussian functions: f1,f2 of the form f1 = a1*Exp[-t^2/s1^2]. Total area, Atot of (f1+f2) is known. Height of each peak (a1 and a2) is known (experimental ...
65 views

### Running file with some extension

I want to run the Mathematica file with some extension, like '.m'. But, I don't know, how can I run the code. Please, guide me.
54 views

### Efficient Round edition with different rounding direction

As pointed out in this post, Mathematica has a special version of Round that Round rounds numbers of the form x.5 toward the nearest even integer. A comment by ...
51 views

### How do I obtain the characteristics and properties of an alloy? [on hold]

I would like to obtain the characteristics and properties of the Alloy Chromel. How do I download that information from the database of Wolfram Alpha and then print it in a Mathematica Notebook? ...
81 views

### How to solve these ODEs using NDSolve?

I have six odes and I cannot use DSolve. So I tried NDSolve. But it says there may be some errors.The code is such like this: ...
42 views

### Custom alignment for GeoMarkers

I need to align a GeoMarker at the bottom left of the marker: ...
152 views

### Dot product result has wrong dimension

I'm doing a small project and I've encountered a problem while using Mathematica. I should mention that I'm kinda new to this software, so maybe it's just something I haven't grasped yet. Anyway, I ...
66 views

### Unable to evaluate Eigenvalues and Eigenvectors for a matrix (2)

I have posted a similar question last year pertaining to this issue. Here's a link to my post together with the solution given: Unable to evaluate Eigenvalues and Eigenvectors for a matrix I have ...
88 views

### A single argument pattern definition applies to multiple-argument patterns?

Consider defining a pattern rule, such as myFun[x_]:=x As far as I understand Mathematica syntax, this rule means ...
41 views

### Rational numbers treated as symbols? How to query for actual symbols? [on hold]

I have noticed that the following query returns FreeQ[Rational[3, 8], _Symbol] False which can only be explained by the ...
46 views

### Extracting parts of an expression

I have lists with expressions like this one: {-DTMomentum2[{0, 0, 1}], DTMomentum2[{0, 0, 0}]}. DTMomentum2 is just an undefined ...
122 views

### Maxwell construction problem with FindRoot

A Maxwell construction is just an integral of area and then solving for a root to find vapor pressure. This must be exactly the same value as where the Gibbs energy plot crosses at a point. I found ...
47 views

### Solve a complex equation symbolically?

I try to solve this equation symbolically: Solve[A*s - b*Log[Sqrt[(d - e*s)^2 + 1] + d - e*s] - x + b*c == 0, s] (yes: ^2 = cntrl-6) But M. (trial version) is ...
46 views

### Numerical Minimization of Large Expression

I want to minimize a function which contains ArcTan functions. The function is also very complicated. I have the following code. ...
57 views

### How can I add labels to a plot?

I have created five lines in a plot. Plot[Table[1 + (k - 1)*Sin[theta]^2, {k, 0, 2, 0.5}], {theta, 0, Pi/2}, PlotRange -> {{0, Pi/2}, {0, 2}}] And I want to ...
59 views

### Dynamically evaluating integrals where the limits of integration must be found with FindRoot

I've the following problem: I need to use Manipluate to scroll over different values for $\text{R}$ ($0<\text{Rb}\le10^5$) and plotting for values of $0<\text{c}<10$. So, I have the ...
101 views
+150

### Solving for coefficients of a polynomial ansatz in a rational function

Firstly, I apologise for the numerical messiness, and for the extended length of this question. If this is successful, this is the last question I will need to ask for a long time. I start with a ...