# All Questions

113 views

### How to draw a picture like this?

That is what l want,but l can only use Show,Plot3D to get something just like this What should l do?Thanks~
352 views

### Does NRoots own an abstract counterpart? If not, can we write one?

We know when solving linear algebra equations, despite its abstract syntax, LinearSolve is much faster compared to Solve: ...
58 views

### Searching if a directory exists within a folder

I hope this question is not a duplicate, but I could not find any other question which answered my specific question, which is: I have the following folder structure (just an example): samefolder/...
155 views

### Small mismatch in theoretical vs MMA solutions of a damped harmonic oscillator differential equation

I solved the differential equation $$\ddot y + 0.43 \dot y + y =0.1 \cos(2x), \quad y(0)=1,\ \dot y(0)=1 \quad(0)$$ using both the theoretical results from wikipedia and using MMA (I also tested ...
498 views

### How to solve the equation $A \sin x + B \cos x = 0$ for all $x$?

I have the equation: $A \sin x + B \cos[x] = 0$ that should be satisfied for all the $x$. Of course, the solution is obvious: $A=B=0$, but I need Mathematica to resolve it automatically because this ...
748 views

### Calculating weird numbers

A weird number is a number such that the sum of the proper divisors (divisors including 1 but not itself) of the number is greater than the number, but no subset of these divisors sums to to ...
416 views

### Trying to calculate derivatives of spherical harmonics

I am trying to confirm what is shown on this website: http://functions.wolfram.com/Polynomials/SphericalHarmonicY/20/01/01/0001/ But when I type ...
163 views

### Indexed Thread on dataset and list

I currently have a dataset, and I would like to add a column based on another list. For example: ...
69 views

### How to edit a list according to the other list? [duplicate]

Gday guys. This problem troubles me, and I hope you can help me solve it. Say I have two random lists L1={{2},{5},{1},{0},{4},{7},{8}} L2={2,5,1,0,4,7,8} and ...
83 views

### Correct interpretation of /. (ReplaceAll)

Consider that you have a complicated expression, which is expensive in terms of running time and memory, and depends on some (initial) parameters. You want to test it for some simple values of the ...
1k views

### How I calculate the volume of multiple intersecting spheres?

I would like to know how to calculate the volume of the union of multiple possibly intersecting spheres (using Sphere[]). Please see the figure: I was trying to get a mesh/delaunayMesh out of the ...
179 views

### Setting value of a rule

How do I change the value of a rule? For example, If I have a = x->3, how do I reset the value of x/.a to 4, so that ...
50 views

### Mathematica defines a function as list

This might be a very silly question but i'm defining a function as: \[Chi][AR_] := ((AR^(2) - 1)/(AR^(2) + 1)); which is clearly a scalar function of AR; however ...
126 views

### position of rows (or columns) whose elements all satisfy a condition

How do I determine the position of rows whose entries all satisfy some condition (e.g., all elements of the row are positive)? I've found out how to use Select to ...
217 views

### How to use select and map together

I have two lists, list1 and list2. I want to Select from ...
103 views

### Is there a convenient way to sum TimeSeries objects in Mathematica?

Imagine I have two TimeSeries objects, ...
128 views

### Can you explain how the remote kernel work

I have use remote kernel almost every day, but I guess I never understand how it works. I have basically two questions: How do we manually setup and use one kernel as a remote kernel to the other? ...
233 views

### Why won't this graph? [closed]

I'm trying to sketch level curve for z=k for the specified values of k={-2,-1,2} of z= 4x^2 - 4x + y^2 + 2y So I changed this(...
137 views

### HSQLDB database webserver access

I need a database that runs its connection over http and not tcpip. The "HSQLDB (webserver)" jdbc driver should be able to do just that. The following code launces the webserver but the OpenSQLConnect ...
86 views

### Can I define a “total Curl” operator similar to a “total derivative (Dt)” operator? [duplicate]

I am trying to take the curl of a vector field. A={A1,A2,A3} B=Curl[A,{x,y,z}] This yields {0,0,0} because Mathematica ...
283 views

### Possible bug: Quantity[2,“meters”] returns 2 None meters

Bug introduced in version 10 or earlier and fixed in version 10.0.2 I'm using 10.0 for Linux. Trial 1: Quantity[2,"meters"] 2 None meters Trial 2: ...
197 views

### How do I get all the roots within a certain range for an equation? [duplicate]

I wish to find ALL the roots of the following equation $x \tan(ax) - c = 0$ within a range, where a and c are constants I control. I've been using ...
173 views

When I plot ...
93 views

### Export as Table with alignment?

I have a table in Mathematica as a list of lists. How to export the table, and force Mathematica to insert as many spaces as needed between columns so that columns are aligned? For example, ...
242 views

### NSolve fails to solve a nonlinear equation

Mathematica can not solve this: g = 9.82; ω = 0.5; h = 5; y0 = 1; v = 0; τ = 0; NSolve[h + v t - (g t^2)/2 == y0 Sin[ω t], t]; The error code is: NSolve::...
69 views

### BarLegend rasterized in EMF and EPS export

A while ago you guys gave me a splendid workaround to the rasterization bug in exported BarCharts. Now I noticed that the workaround is not working for BarLegends. My problem is, that ...
144 views

### Integrate over implicit 1D region: works for algebraic but not transcendental equation?

QUESTION How come this works: NIntegrate[1, {x, y} ∈ ImplicitRegion[{x == y^3, x <= 1, x >= 0}, {x, y}]] But this fails: ...
210 views

### Convert recursive RegularExpression to StringExpression?

Consider the following expression for matching balanced brackets: ...
220 views

### Export generated mesh

Say I have generated a mesh using ToElementMesh, following one of the examples here: http://reference.wolfram.com/language/FEMDocumentation/ref/ToElementMesh.html ...
206 views

98 views

### Black Ovals appeared in my Mathematica notebook [duplicate]

I copied and pasted something from another Mathematic notebook and started getting the same black ovals seen in this question: Colored marks appearing in notebook input text? The suggestion to turn ...
92 views

### Is there a documentation generator for Mathematica?

I'm looking for a way to document the functions of my packages inline, preferably inside comments. There should be a Doxygen type tool for this that takes comments and that generates html from markup ...
31 views

### Changing cell style in V10.0.2 [duplicate]

In Mathematica 10.0.0 and 10.0.1 I used to change cell style by putting the cursor anywhere in the cell and then invoking one the short cuts (Alt + 1, 2, 3, 4, 5, 6, 7, 8, 9) to change cell style ...
195 views

### How to move a cell up or down with a keystroke?

It is very useful during refactoring to move lines around. All popular IDEs or text editors have this feature (PyCharm, Vim, Sublime, etc..) for example in Xcode you press: ⌥⌘[ or ⌥⌘] to move lines up ...
102 views

### Does FindFit use symbolic differentiation?

Does FindFit use symbolic differentiation when optimizing by least squares a non-linear function?
57 views

### How to import (from a table file) only rows with a specific element in a given position using Import?

I have a large file containing a table. To be specific, the table columns are aligned by spaces, and the rows are terminated by newlines. I want to import only specific rows from this table. For ...
30 views

### How to specify alignment of columns when exporting a table using Export, and how to use spaces instead of tabs?

I have a table in list representation. How can I export it, specifying that some columns must be right-aligned and others left-aligned? Morevoer, columns should be space-separated (with an appropriate ...
90 views

### How to list indices of list elements that meet a condition? [closed]

Is there a tidy way to create a list of the indices of elements of a list that meet specified conditions? This method gets the job done, but it's clumsy and not conducive to nesting: ...