6
votes
3answers
383 views

Finding connected components in an array

I have an $w\times h$ array with non-negative integers. I wish to partition the set of coordinates $(c,r)$ with $1\leq c \leq w$ and $1\leq r \leq h$, in subsets, so that each subset corresponds to a ...
7
votes
1answer
257 views

Variable scoping in Module

I don't understand why $a$ and $b$ are not local in the following code: ...
2
votes
1answer
134 views

Deriving least-squares equations in Mathematica

I define $Y = a + b*x + e$, and I want to find values for $a,b,$ by least squares, so I minimize $RSS = sum((Y_i - a - b*x_i)^2)$ I then take derivatives, ${d RSS \over da} = 0$ and ${d RSS \over db} ...
3
votes
0answers
65 views

Why doesn't ReplaceAll work on Image? [duplicate]

ReplaceAll seems not to reach inside Image, and I don't see why it shouldn't. Here is an example. Create a black and white image ...
3
votes
1answer
233 views

Integrate equations of motion when force depends on position

I'm fairly new to Mathematica. I'm trying to test my C++ implementation of a fourth order Runge Kutta method for Newton's equations of motion. I want to test my integrator when the applied force is ...
0
votes
0answers
225 views

Interpolation of multidimensional data organized logarithmically

The following threads call our attention to the fact that "accuracy of Interpolation will be worse with an unstructured grid", in the context of interpolation of 3d data: interpolation of 3D data ...
0
votes
0answers
17 views

Restoring a Mathematica session without notebook interface [duplicate]

It happens all the time that I close my Mathematica session and later I regret that I have done so, because there are many things that I would like to check. I would like to know if there is a way to ...
5
votes
1answer
358 views

Mathematica scripting on Microsoft Windows

Is it possible to use Mathematica (or the Mathematica kernel) to interact with Microsoft Windows, much like any macro-based scripting language that controls the keyboard/mouse, opens/closes programs ...
0
votes
1answer
104 views

Replicating Excel output using Mathematica

I have 2 columns of data in Excel. One is inputs the other is outputs. I ask Excel to make a graph of that data and to fit the data to a power trendline. Excel does this and it's fine as far as it ...
0
votes
0answers
97 views

Local variable names - Is there an easy way?

I apologize first, because this has been asked, like in Treat all variables as local in a module [duplicate] Variable scope similar to other languages But I don't get how to use them. Some codes ...
10
votes
1answer
3k views

How to solve a system of partial differential equations?

Edit: since the upgrade to Mathematica 10, this problem seems solved I just want to solve a system of partial differential equations, for example: $$ \left\{ \begin{array}{l} ...
2
votes
2answers
119 views

Testing for arbitrary algebraic expression in given variable

I want to test, for example with MatchQ, if the argument of a function is an arbitrary expression in a single or several variables whose names can be assumed to be ...
1
vote
1answer
255 views

Boundary condition is not specified on a single edge of the boundary of the domain

I am attempting to solve a PDE as prescribed in a paper I am reading; however, Mathematica doesn't seem to be happy with the way I am posing the problem. Im my case, r(t,100) is an approximation of ...
4
votes
2answers
105 views

Problem with ViewVector

I am trying to have a satellite (camera) move around the earth (unit sphere) and take picture of the earth. The satellite keeps constant distance from the earth, and always looks toward earth center. ...
2
votes
0answers
81 views

Problem with files size

I need to work with long time series, but I notice that this generates huge files that Mathematica doesn't handle well at all: even opening/saving one of this files is difficult, and the kernel quits ...
0
votes
1answer
67 views

Excluding an interval of parameters from Integrate [duplicate]

I'd like to compute an integral that depends on a parameter, but I'd like to exclude an interval from the computation. For concreteness, say I want to compute ...
20
votes
6answers
3k views

Finding the intersection of a curve with an interpolation function

There are no issues trying to find the intersection points of two defined curves. ...
1
vote
2answers
139 views

Symbolic solution of system

everyone! I am sorry, but I am an abcolute novice of Mathematica (to be more precise this is my first day of using it) and even after surfing the web and all documents I am not able to solve the ...
1
vote
1answer
105 views

Use Simplify option Trig->False when 3rd argument to Collect is Simplify

I would like to simplify the following expression AAA (4 Sin[x]^2 Cos[x]^2) + AAA 4 Sin[x] Cos[x] + AAA with the ...
0
votes
0answers
38 views

Faster evaluation of an expression for brute force optimization [duplicate]

I'm trying to bruteforce an optimization problem and I want to generate roughly a million function evaluations. I was wondering what would be the best for me to do in terms of having the expressions ...
-1
votes
2answers
84 views

Can I tell Simplify to prefer nested polynomials?

I need to export expressions for numerical evaluations in a C codebase. Simplify often does a good job for this, and polynomial factorisation goes a long way. However, occasionally I would come ...
3
votes
5answers
417 views

Minimum in a nested list [duplicate]

I have a nested list of {x,y,z} and I want to find out the values of x and y where z is minimum. I can write a nested For loop and do it ...
4
votes
1answer
91 views

Add options to upvalues

I have some objects that I want to present in TeXForm. Thus, it is easily to do as follows: YoungTableau/:TeXForm[YoungTableau[diagram_]] However, what if I ...
5
votes
3answers
194 views

Non-descending Tuples

I want to get all the non-descending tuples of a list with given length, for example: f[{1,2,3,4},{3}] ...
4
votes
2answers
488 views

specify field width in Print

I would like to format the output. For example, the following code gives ...
8
votes
1answer
330 views

How does PlotLegends actually work with ListPlot3D?

I'm sensing this might be a rookie mistake but normally I roll my own legends but decided to try the built in legends for a ListPlot3D. ...
1
vote
2answers
248 views

Replace a column in table with a list of numbers?

I have a Table of values e.g. {{x,y,z},{x,y,z},{x,y,z}…} How do I replace the the "z" column with a List of values?
2
votes
1answer
318 views

Infinite loop with While is very processor-intensive [closed]

This simple line of code: While[True, Pause[1]] uses 55% of one CPU core on my computer. Are there more efficient ways to construct simple infinite loops in ...
0
votes
0answers
42 views

Using Table[ ] vs using Do[Append [ ] ] [duplicate]

Is it generally better/faster to use the Table function over using Do[Append []]? For example, I have this piece of code: ...
7
votes
1answer
311 views

Visualize a tree structure using TreeGraph

I have a code that generates a tree of graphics objects. The structure can be visualized like this, with each Rule constituting a parent child relationship: ...
2
votes
3answers
89 views

Assigning symbolic operators to built-in functions

Can I do something like this: $$\partial_t = D[f, t]$$ i.e. create a symbol instead of a function so that each time I call it, it executes the operation as defined?
2
votes
2answers
202 views

Checking if a number is a perfect power

I wanted to know how would I use Mathematica in order to check if the number is a perfect power I saw the algorithm but couldn't grasp it enough to implement it, so can anybody help?
1
vote
0answers
157 views

Invert a transcendental function

I have tried Reduce and Solve in Mathematica, as well as have a long list of tries in Maple, but cannot seem to get anywhere ...
0
votes
0answers
183 views

How to plot an implicit equation with separate dispersion lines of Lamb waves

I'd like to plot (to try reproduce) dispersion curves of Lamb waves as in http://en.wikipedia.org/wiki/Lamb_waves But I can't to separate each lines. I was reduce the dispersion equations as X=ωd/Vs, ...
0
votes
1answer
369 views

Pass unevaluated function with evaluated arguments

I am almost sure that this question has been asked somewhere. I found similar ones, but I cannot find exactly what I need, which might mean that I am on the wrong track. I search a method to pass an ...
0
votes
0answers
103 views

Probability Model

I have the following probability model: $(X_k|\text{ PastHistory}_{k-1}, \theta_0, \theta_1, \theta_2) \sim (\pi\cdot N(\theta_1+\theta_0\cdot X_{k-1},1)+(1-\pi)\cdot N(\theta_2+\theta_0\cdot ...
1
vote
1answer
60 views

Palette to set Cell Options such as Background Editable and Initialization property?

Hello I have found examples of codes that generate palettes to format the text of a cell (or a portion of it). I have also found codes for palettes that change the style of a cell. The latter is ...
2
votes
3answers
219 views
0
votes
0answers
86 views

eigenvalues and eigenvectors without Root answers

I'd like to find eigen values and vectors of parametric 21*21 Matrix and i cant solve the root problem.please help me to find the answers without Root. My Matrix is: ...
-1
votes
1answer
163 views

ListLinePlot problem

OK, so here I got the solution of a numerically-solved PDE. I wish to plot in a graph, for a given time, the point x where the solution reaches 1/2. So here's the relevant string of code: ...
3
votes
3answers
259 views

Fastest way to check if an expression contains all symbols from a list

I need to execute this function thousands of times, and the faster, the better. I came up with two versions, but wanted to see if you can come up with an even faster way. Is there a better way? I use ...
4
votes
1answer
246 views

replace items in a list with items in a another list

Suppose I have a list A={x1,x2,x3}, a list B={3,4,5}, and a function f[x]=x1+x2+x3. Is there ...
0
votes
0answers
75 views

3d graphic for publication [duplicate]

Journals are very strict and some of them require special formats. They suggest the .tiff or .jpg format for graphics with many colors. I have problem how to export, for example, this figure consists ...
9
votes
2answers
459 views

Rearranging a List

I am trying to rearrange/sort a list i.e. {{1,2},{10,140},{43,10},{1,140},{43,2}} into ...
8
votes
1answer
249 views

Defining my own invisible operator

There are some invisible operators in Mathematica (\[ImplicitPlus],\[InvisibleTimes],...
2
votes
0answers
38 views

Am I using the cell option setting PageBreakWithinGroup->False correctly?

I had expected that this option would prevent a page break occurring within a group of cells of which this cell is the "group leader". In my case it is a "Subsubsection" containing a group of ...
5
votes
0answers
119 views

NMinimize seems to call function with the same values multiple times

I have to minimize a function where the evaluation of one parameter set takes very long (around 5sec) and discovered alongside, that NMinimize seems to call this ...
3
votes
0answers
47 views

Tick labels above axis [duplicate]

Is there any way to place tick marks on the x-axis above the axis? Note that I am talking about marks on the axis, not on a frame (because my graph has no frame). To be more specific, here's the ...
1
vote
1answer
328 views

Problem With 3D Contour Plot

So I am very new to Mathematica and I'm using version 9. I need to plot a function $f(x,y)$ such that $f(x,y)$ is equal to $y^2$ when $x > y$ and equal to $10 \sin(x)$ when $x < y$. I want two ...
20
votes
1answer
325 views

Highlight Pie in PieChart

PieChart has the nice functionality of highlighting a single pie when you click on it. It is then sticking out a little. See the following example: ...

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