All Questions

2
votes
3answers
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: ...
1
vote
1answer
51 views

Attaching independent variable values to data for curve fitting

I have a data set of $10^4$ entries. I want to plot the last $2000$ data with the same argument at $x$ axis and fit a curve. That means the range of $x$ axis will be $8001$ to $10000$ incremented by $...
0
votes
2answers
45 views

How to force simplify to drop common denominator in inequalities?

Simplify[c>0 && a/c <= b/c] results in c > 0 && a <= b, as hoped. However when ...
5
votes
1answer
273 views

Extraneous elements in “Europe countries” list [on hold]

I found that the list "Europe countries" encloses "Russia" and "Moldova". This is not correct! Any hint?
1
vote
2answers
37 views

Extracting numerical value from sentiment classifier

I have this code, and want to extract out just the number. I tried QuantityMagnitude and a transformation rule. ...
17
votes
1answer
993 views

Animating wave motion in water

Further to this question I found on MSE, I tried to replicate from here this is as far as I got: ...
3
votes
2answers
99 views

Heat equation with variable conductivity

Let us consider the (very simple) problem $\qquad \partial_x[k(x)\,\partial_xu]=0,\quad x\in [0,1]$ $\qquad u(0)=0,\ u(1)=1,$ with $l\in(0,1)$ $\qquad k(x)=\left\{\begin{array}{l}k_1^{},x<l\\k_2^...
0
votes
0answers
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 ...
4
votes
1answer
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)+...
2
votes
0answers
44 views
1
vote
0answers
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....
0
votes
0answers
32 views

Amplifier adder [on hold]

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, ...
8
votes
2answers
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. ...
-1
votes
2answers
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 ...
0
votes
1answer
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,...
0
votes
1answer
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 ...
0
votes
0answers
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. ...
1
vote
0answers
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 ...
3
votes
1answer
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 ...
5
votes
1answer
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 ...
0
votes
1answer
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 ...
0
votes
0answers
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?
0
votes
3answers
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...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
1
vote
1answer
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, ...
1
vote
0answers
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: ...
0
votes
0answers
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 ...
10
votes
1answer
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 & ...
3
votes
1answer
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 ...
4
votes
5answers
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 ...
0
votes
1answer
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 ...
3
votes
1answer
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.
1
vote
1answer
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 ...
0
votes
1answer
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? ...
3
votes
2answers
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: ...
6
votes
1answer
42 views

Custom alignment for GeoMarkers

I need to align a GeoMarker at the bottom left of the marker: ...
2
votes
4answers
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 ...
2
votes
2answers
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 ...
4
votes
1answer
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 ...
0
votes
0answers
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 ...
0
votes
1answer
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 ...
6
votes
1answer
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 ...
0
votes
1answer
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 ...
1
vote
2answers
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. ...
1
vote
1answer
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 ...
0
votes
1answer
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 ...
0
votes
0answers
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 ...
1
vote
0answers
72 views

Design completion idea for Position [on hold]

This is not exactly a question but rather a suggestion for a design which I think would greatly improve Mathematica. Before I put this to Wolfram Research I would like to see what other people think ...
0
votes
0answers
37 views

Wolfram CDF Player Pro trial license [on hold]

Is there a Wolfram Player Pro trial (e.g. for limited time) license available?

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