# All Questions

8 views

### Changing the length of the vectors in vectorplot

I have the following code, and I've tried almost everything I can think of, even VectorColorFunction to describe magnitude. I am trying to make the length of the vectors proportional to r^{-2}, and ...
19 views

### Real Analysis question [on hold]

Question: If n in N and f(x)=x^n, negative infinity < x < positive infinity, prove that f is continuous at each point in R. Could anyone help me with this to prove? I am lost :( Thank you in ...
21 views

### How do I bandpass a signal in Mathematica 8

I would like to use the bandpassing function that is available in newer versions of Mathematica but not Mathematica 8: ...
35 views

### Second order differential equation

Hey guys I need someone to give me a hand on this. I don't know if this is too complicated or it's just the lack of knowledge I have on Mathematica. I'm trying to solve the following equation but ...
56 views

### Maximize violating constraints

I have Maximize[{(h*10)/(300*(100 - (l^.5 + d^.4 + H^.6))), (l + d + H + h) == 669, l > 0, d > 0, H > 0, h > 0}, {h, l, d, H}] I believe ...
52 views

I was trying to solve the initial value problem $$u'(t) = \sqrt{u(t)} + \frac{1}{n+1}, \, u(0) = 0$$ using DSolve: ...
73 views

### Solving with DSolve recursively

I need to find $f(x,n)$ in the interval [0,1] defined by recursion, $$\frac{d f(x,n+1)}{dx} = f(x,n)$$ with boundary conditions $f(0,n+1) = 1$ and $f(x,0)=1+ x$ Using ...
42 views

### ListContourPlot is blank

This is probably very simple. I want to do a simple ListContourPlot. ...
105 views

### Splitting strings into letter keys and integers

I have strings of the following form: string = "ABC123DEFG456HI89UZXX1"; Letter keys of variable lengths are followed by (positive) integers. I want to get this ...
156 views

### Efficient method to generate Tridiagonal 50 by 50 Matrix?

I'm looking to generate a tridiagonal 50x50 matrix, ideally without using loops. Suggestions on most efficient code for this?
76 views

### Incorrect result with SemanticImport

I might use this incorrectly. I want to use a .csv file that as list looks {{"Group", "data 1", "data 2"}, {"a", 1, 5}, {"a", 2, 3}, {"a", 4, 5}, {"b", 8, 9}} ...
57 views

### Random symmetric matrix

Suppose first that I want to generate a matrix whose elements are i.i.d. with distribution dist. This is easy: ...
64 views

### Creating a table giving the statistics of random polynomials

I already have a formula for generating random polynomials as well as for counting the real roots of every polynomial (see my previous question). But now I face the problem of how to organize the ...
161 views

### Why can't a string be formed by head String?

Since everything is an expression in Mathematica, why must a string object be formed by "abc" but not by a String[abc] ...
78 views

### Determining the range of parameters that yield real values for a certain NIntegrate form

I have specified just one set of $s$ and $g$ values that yields a real value for the NIntegrate below. It is possible that some $s,g$ combination can give rise to ...
66 views

### The value of ln(1-I)+ln(1+I) [on hold]

These are the values Wolfram Alpha gives: (1-I)*(1+I) = 2 ln((1-I)*(1+I)) = ln(2) ln(1-I)+ln(1+I) = 2 Can someone please explain this? Does Mathematica give the ...
23 views

### Problem with running mathematica script involving Export on cygwin [on hold]

I am trying to run the following script on cygwin : ...
76 views

### Why does LinearSolve return the transpose of the answer matrix?

I am trying to solve an equation of the form $dv=F\cdot dV$ where $dv$ and $dV$ are matrices derived from the row vectors $dx$, $dy$, $dz$ and $dX$, $dY$, $dZ$ respectively. If it helps, $F$ is the ...
26 views

### Is there any possible to change the time step size according to a series of WhenEvent or any other method?

As the title, I want to explicitly decrease time step with the evolution of system. I tried the following code, and adopt ImplicitRungeKutta method to integrate with respect to time. But I can only ...
41 views

### Solution of differential equation in terms of incomplete gamma function

I need help in solving equation 15 and 16 either manually or in Mathematica to get the solution in terms of the incomplete gamma function. This is what Mathematica tells me. I can't understand ...
46 views

### Any packages for vertex enumeration on Mathematica?

My work requires me to enumerate all vertices of a polytope defined by linear inequalities from time to time. And I'm mainly working with _Mathematica 9.0 on Mac OS X 10.9. So I wonder are there any ...
69 views

### Is Object Oriented Programming paradigm still necessary in Mathematica? [on hold]

OK, this problem is more close to philosophy. People program in C++, Java and C#, etc, always think OOP to be a divine and inevitable programming paradigm to make a large project easy to build, to ...
59 views

### Generalize WASD Function First Person Viewing

How might I generalize the following WASD question such that it works with any Graphics3D object and includes q and ...
73 views

### How would I input this truth table into Mathematica or Wolfram Alpha

I am unsure how to put the negations after a gate or before a gate?
154 views

### Accurately distort graphics

I would like to accurately distort this plot of $\sin(x^{1/2})$ (and others like it) so that the wavelengths are evened out (ie - "inverse-square root" it). I should like to do the same to "de-log" ...
88 views

### How to test for Indeterminate values?

I need something like this a = 101010/0; If[a == ComplexInfinity, True, False] But if I use ToString, I get what I want. ...
36 views

### How to pattern match an association? [duplicate]

I have the following: Clear[a, b]; a = {{1, 2, 3}, {4, 2, 5}, {6, 7, 8}}; b = GroupBy[a, #[[2]] &]; b whose output is: ...
57 views

### Solving a system of DAE on mathematica

I am having trouble solving a system of Differential Algebraic equations of mathematica, the solution I get is just zeros although it should give me an answer, here is my code: ...
71 views

### Change font of formula number in DisplayFormulaNumbered

I am trying to change the font of the formula number in a cell which has style DisplayFormulaNumbered. I can easily change the font of the formula I enter by selecting it and using the format menu. ...
42 views

### Compile issues, scoping and order of evaluation

I have a few questions about compiling functions, which I think are all related to scoping and order of evaluation. I will illustrate them by a minimal example of the problem I have. I'm sorry for ...
56 views

### How to remove selected wire frames from bounding box in 3D plots?

In 3D plots one can eventually hide the whole bounding box by the use of option Boxed -> False. How to remove only a selected part of the wire frame that ...
57 views

### Probability evaluation fails with equals condition

The following evaluation fails (the result is just the copy of the input) \text{Probability}[0<x\leq a | x-y=t,\{x\ {ExponentialDistribution}[\lambda ],y\ {ExponentialDistribution}[\lambda ...
183 views

### How to count number of observations/rows within each group

I have a huge unbalanced panel data. I want to count number of rows within each group. For example, I have the following data: ...
181 views

### Multiple Forms of Transportation Between Cities

I want to be able to show different connections between cities based on modes of transportation. For instance, you could walk to any city, but it would take a long time, you could take a train, but ...
384 views

### Composition à la Mondrian

I would like to paint something like this or,even better, like this I have tried ...
38 views

### Changing face as you type in an expression in notebook

I've a Mathematica notebook for my class notes. When writing plain text in cells, I can dynamically bold and unbold with the ctrl+b shortcut. However, when in a mathematical expression, this shortcut ...
49 views

### How to use initial fixed timestep, then decrease it according to dependent variable, while spatial stepsize is fixed

I am trying to solve an advection equation. I want to force constant spatial step size (x dimension) with the “MethodOfLines” option, whereas I want to use initially fixed time step size 0.01 then ...
54 views

### Binning of listplot [duplicate]

I have two arrays describing a 1-dimensional mass distribution. The first array, $x$, are the (un-sorted, and un-evenly distributed) x-coordinates; the second, $m$, the corresponding masses. I would ...
110 views

### Converting a matlab program into Mathematica 10

I sought help from this entry at Calling MATLAB from Mathematica to see if I could CONVERT a mathlab program which simulates polymer dynamics that is provided at the download section at ...
76 views

### Why I can not get the plot when I use NDSolveProcessSolutions?

Why I can not get the plot when I use NDSolveProcessSolutions? Anyone can give me a clue. Thanks a lot! ...
42 views

### Improving working precision of LegendreP[n,x]? [duplicate]

I was trying to evaluate N[LegendreP[5,0.1]] The cell gives me: N[LegendreP[5,0.1]]=0.178829 However I wanted more ...
52 views

### Removing the unit “pm” from atomic positions [duplicate]

The following input yields an output with the unit pm (0.01 Angstroms), how do you eliminate this unit so that only numbers are generated. ...
44 views

### DeleteMissing level spec confusion [duplicate]

Given: titanic = ExampleData[{"Dataset", "Titanic"}] Why does this correctly delete Missing[] elements: ...
560 views

### Mathematica isn't sure whether a sum of two positives is positive or not

Mathematica is not able to tell whether a summation of two positive expressions is positive or not. Which is very strange. My three symbolic arguments, $x$, $y$, and $z$, are all real numbers bounded ...
42 views

### Axis Labels Disappear With Manipulate

I have a ListPlot3D with custom axis labels that I am scrolling with Manipulate. My issue is that the axis labels scroll away as ...
72 views

### Is there a change in V10 with Solve and exponents?

I've encountered a strange problem with V10. I can't quite nail it down, but the Solve seems to be unable to solve equations that it could in previous versions. ...
55 views

### How to figure out whether a nonlinear inequality holds or not

I have an inequality consisted only of seven parameters as follows: $(1 + g)^{-(m+w)}\big[\big\{a+(1-a)(1 + g)^m\big\}(1 + p q)Q - (1 + g)^w \big\{(1 + g)^m (1 + q)-(1-p)q\big\} Q\big] < 0$ ...
39 views

I have a library function that need to load some external data files. But it looks that the path in the default path of library function is the path that Mathematica is currently in. Is there a way ...