2
votes
4answers
176 views

Given a matrix of integer, create a matrix with 1 or 0 according to which numbers are in the first matrix

Not sure the title gives the idea of what I need, so here is a sample: I have ten (w) combinations (subsets) of 20 (n) numbers taken 4 (k) at time. I need a matrix of dimension w x n with 0/1 in each ...
4
votes
1answer
137 views

Split/unmerge merged cells in notebook file

I have merged cells in a Notebook file. Is there a way to split such a merged cell group back to single cells, in each of them being one command?
0
votes
2answers
70 views

NSolve not solving [closed]

I've been working on a Newton Cooling equation problem for my diff equ class and cannot get NSolve to solve this equation. I've plugged it into Wolfram Alpha and my ...
1
vote
1answer
249 views

How to solve time dependent coupled differential equations using Floquet method?

I have coupled differential equations D[X[t], t] == M[t] X[t] + R[t] where ...
2
votes
1answer
144 views

Large data -list contour plot -list log plot

I've a large data make matrix 100*100 and and other two sets of data represent the x and y axis. Each value in the matrix is a related to one value in x and one value of y. I ask about a way to plot ...
0
votes
1answer
89 views

Displaying Greek letters with subscripts inside plot [duplicate]

I am using ListPlot: ...
6
votes
4answers
911 views

Finding number of pixels with certain RGB color in an image

I have the following image: To determine the number of black pixels (nBlackPixels) I use: ...
0
votes
1answer
77 views

How can I move the x-axis label beneath (instead of at the end of) the x-axis?

I borrowed this code from a Wolfram demo. I looked at several answers to the general question of how to move the x-axis label from the end of the x-axis to beneath it (use ...
0
votes
2answers
122 views

Write list of numbers to a file

I have a list of numbers: e.g. list={1,2,3,4,5} To write the list to a file I use (here each integer number occupies 7 spaces): ...
0
votes
1answer
52 views

Plotting based on all previous equation results [closed]

I have a plot Plot[40500*x^(-0.1), {x, 1, 100}, PlotRange -> {0, 50000}] Now, I am trying to plot the cumulative of these y values. I'll try to explain on an ...
2
votes
1answer
163 views

How to convert a rational parametric plane curve into implicit form?

This problem is generated from another Green's theorem related question of mine. And here is a forward of the same problem in math.stackexchange. The original equation of the plane curve is not in ...
3
votes
4answers
481 views

How to Find “n” for n-th Triangular Number

For example, the 7th triangular number is 28. How do I create something that will tell me that 28 is the 7th triangular number? This is what I have created. ...
17
votes
1answer
339 views

How can I smooth a 3D surface generated by RegionBoundary?

I have a set of points that belong to the surface of an object. I would like to approximate a surface to which I can compute the distance. of other points. With the nice code of this post, I was able ...
1
vote
1answer
200 views

How can I convert a fraction to a string that can be used in a file name?

I want add an index to the file names of my exported images, so I'm using ToString. But I have a problem when my index is a fraction, because then the generated ...
1
vote
1answer
103 views

Mathematica computes wrong eigenvectors? [closed]

I have a matrix M = {{0, 0, 0, 0}, {0, 0, 0, 0}, {0, 0, 0, b}, {0, 0, -b, 0}} that I want to diagonalize. So far, I always used the following and it worked, but ...
6
votes
2answers
184 views

How to Write Partition with Infix?

The documentation says that using Infix ~, the following input f[e1,e2,e3,...] can be rewritten as ...
0
votes
2answers
178 views

Problem with NDSolve: derivative interpreted as square [duplicate]

I am using Mathematica 9, and trying to solve a very easy differential equation with NDSolve. The code I have is s=NDSolve[{y'[x]==y[x],y[0]==1},y,{x,0,1}] but I ...
2
votes
1answer
215 views

Help me export high-resolution TIFF figure

I have generated a figure in MMA by ContourPlot3D. How can I export this figure in high-resolution TIFF format(say, 1200 dpi for lines, 300 dpi for halftone and ...
2
votes
1answer
107 views

Error accumulation in NDSolve?

I'm trying to solve this system of ODEs numerically: $$\vec{Q} = \vec{P} \times \vec{Q}$$ where vectors $\vec{P}, \vec{Q}$ have 3 components: $$\vec{Q} = \left( Q_1, Q_2, Q_3 \right) $$ $$\vec{P} = \...
2
votes
2answers
76 views

Notebook cells space on disk profiler

I have one single notebook with more than 500 mb... To control its growth, I would like to have a profiler of used space (not the live memory, but the space on disk), in such a way that I can easily ...
4
votes
2answers
136 views

Simplifying expression with non-commutating entries

Say I have an expression such as (a + X)**(b-Y) where the variables above possess the following commutation relations [a, b] = [a, X] = [a, Y] = [b, X] = [b, Y] =...
3
votes
0answers
54 views

Why does FreeQ seem not to work with complex numbers?

I guess I do not understand how Mathematica evaluates this simple expression inside FreeQ ...
6
votes
1answer
211 views
7
votes
3answers
350 views

Copy/Pasting a Grid of Numbers from Project Euler

On Project Euler Problem 11 (link: https://projecteuler.net/problem=11), there is a 20x20 grid of numbers. However, when I pasted it into Mathematica, I got this strange result where the times symbol '...
3
votes
3answers
233 views

Matrix with known entries but unknown size [closed]

I am trying to perform some calculations with a matrix that has let's say size N but unknown, please How can I write this in mathematica?
3
votes
1answer
62 views

How can I get the vertex labels of an existing graph?

For example, if there is a graph g = CompleteGraph[5, VertexLabels -> {1 -> "v1", 2 -> "v2", 3 -> "v3", 4 -> "v4", 5 -> "v5"}] How can I later ...
5
votes
2answers
182 views

Can the increment in Manipulate, Table, Range, etc. be subject to an If statement?

In this demonstration I'm working on, I would like to plot a piecewise function with the tangent line to the function at a point that is determined by c in the code ...
3
votes
1answer
149 views

Where can I access documentation for old versions of Mathematica?

Some documentation of functions available in old versions of Mathematica (and old packages) is available online, e.g. http://reference.wolfram.com/language/Combinatorica/ref/Vertices.html Is there ...
3
votes
3answers
184 views

Calculating $\lim_{x\to 1} \, \int -\frac{i \text{Li}_2\left(x-x^2\right)}{\sqrt{3} \left(x-\frac{1}{2}-\frac{i \sqrt{3}}{2}\right)} \, dx$

How can we force Mathematica to compute this limit? $$\lim_{x\to 1} \, \int -\frac{i \text{Li}_2\left(x-x^2\right)}{\sqrt{3} \left(x-\frac{1}{2}-\frac{i \sqrt{3}}{2}\right)} \, dx$$ It seems it ...
2
votes
1answer
92 views

Is there any way to perform an ANOVA test given $n$, $\bar{x}$ and $S^2$?

Suppose I have the following data about the incomes of residents of three cities. $$ \begin{array}{|l|c|c|c|} \hline & n & \bar{x} & S^2 \\ \hline \text{City A} & 10 & 2.8 & ...
2
votes
0answers
135 views

Converting integral equations to differential equations

I am trying to use Mathematica to convert integrals to differential equations, of any order. An example of an integral equation is given below, in Mathematica code. Could you please advise as to the ...
2
votes
2answers
104 views

How to remove multiplicities from for a list in way meeting special criteria

I have a list of pairs, tabul, which has the property that the second element of each pair is also an element in my list data. I ...
18
votes
1answer
1k views

my Mathematica has turned orange and not able to find out why

I do not know what happened. But when I rebooted my PC, now Mathematica comes up orange colored. I shut down the PC and tried again, it is still orange. Here is screen shot: I also did a reset. ...
2
votes
2answers
167 views

Plotting a set of points given by a complex expression [closed]

A have the set consisting of the complex numbers $1+3r \cosθ−ir \sinθ$, where $r∈[0,1]$ and $θ$ may vary between $0$ and $2π$. This is my first encounter with Mathematica, and am having difficulty ...
1
vote
1answer
91 views

Compute complete graph and make minimum spanning tree

I'd like to plot a complete Graph and then compute the Minimum spanning tree of it. I already can make a complete graph out of a list that countrydata gives me: ...
5
votes
2answers
508 views

How to export images in EPS format that can be opened in CorelDraw

I am preparing a paper. The journal requirements are odd: only eps files for pictures are accepted. All pictures I have drawn in Mathematica and exported in eps format in the usual way: ...
0
votes
0answers
88 views

Comments including LaTeX commands in Mathematica [duplicate]

I want to write some comments in Mathematica - which include LaTeX commands - using the form ...
6
votes
1answer
232 views

How to check the option value?

Given that I have a function func as follow: To check the value of options, I using the step-by-step method If[] ...
7
votes
4answers
340 views

How to Apply Functions to Lists with Many Curly Brackets?

For example, consider the list defined below. samplelist = {{{1,2,3,4}}, {{5,6,7,8}}}; How would I apply the Times operator ...
1
vote
1answer
83 views

Functions becoming undefined when evaluated

I'm so confused I don't even know how to phrase my Question title. My function nextCol works until I use colLength, then ...
3
votes
2answers
85 views

Faster use of Condition for a large array (see the example)

Here is the example/problem. I have a array of $n$ random number. n = 2000; p = RandomReal[{0, 9}, n]; I have to create a $n\times n$ sparse matrix with $(i,j)$...
4
votes
3answers
196 views
5
votes
2answers
74 views

Building up a sequence dealing with a complex recursive scheme

Suppose I have multiple lists, the first one contains 2 elements, the next one 4 elements, the next one 8 elements, and so forth. Let these elements be labeled as Gij where i refers to the list it ...
0
votes
0answers
77 views

Optimization over 6 vectors

Suppose I have an expression which depends on 6 unit vectors (3 dimensional). Hence, I need to optimize over 12 parameters (every vector contains 3 parameters, but one we can reduce by considering ...
3
votes
1answer
149 views

How to tell Mathematica that my variable is a scalar

In my calculations I have these combinations PauliMatrix[1].f PauliMatrix[2] where f is a scalar function. The result is as ...
3
votes
1answer
103 views

How to get the size of a specific image in the front end?

The title pretty much says it all. One possible point of confusion is that this question is not limited to items with head Image. I don't know what is the ...
4
votes
2answers
153 views

How to scale multiple graphics to preserve relative sizes?

I'm looking for a simple way to make the displays of different Graphics expressions accurately reflect their relative sizes. (By "simple" I mean that it does not ...
5
votes
3answers
87 views

Conditional subset generation

I am trying to accomplish the following task: Given a list of coordinates of n points in the plane, I need to find subsets of all points that share the same x-...
4
votes
3answers
295 views

Drawing a ladder graph with Line and Table/Array

I want to programmatically draw a ladder graph like the one below: I'd like to use Table to dynamically add steps. My (lame) attempt so far: ...
2
votes
1answer
243 views

Labeling a ListPointPlot3D

I've a problem with the label of ListPointPlot3D. I tried to reproduce a plot I've seen in a paper, but I was not able to reproduce it completely. Following and example of my data: ...

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