6
votes
2answers
120 views

Algorithm in RandomChoice[{w1,w2,…}->{e1,e2,…},n]?

I wonder if someone happens to know the actual algorithm implemented in the particular overload of RandomChoice that handles explicitly presented discrete ...
-1
votes
2answers
205 views

Plotting solutions of differential equations with different parameters [duplicate]

I want to plot x[t], when i manipulate w from 0.1 to 1.5. Here is what I've attempted, which does not work as expected. ...
0
votes
0answers
72 views

How to solve an inequality

I am trying to solve the following inequality: Assuming[{R[k] >= 0, R[k + 1] = R[k] - 2^N Y, Y >= 0 && N >= 0}, Refine[Re[R[k + 1] >= 0]] I ...
1
vote
1answer
181 views

Skewness of distribution vs. skewness of distribution's PDF

I'm having trouble understanding why the skewness of built-in distributions is not the same as the skewness of their probability density functions. For example, the following are different (the first ...
0
votes
1answer
99 views

Plot graphs in different colors

I am generating a set of plots and exploring how changing a parameter affects the plot shape. I want each plot to be a different color, but the color rule i'm applying seems to only work for the last ...
2
votes
2answers
107 views

I'm trying to filter a date range by day of month and day of week - what am I doing wrong?

I am trying to generate a list of dates that match two criteria: they have to all be the first of the month, and they have to be a particular day of the week, Sunday in my case. The code I have ...
1
vote
2answers
294 views

intersection between function and plane

I try to solve a ODE system of equations and i want to plot the intersection of the 3D solutions with a costant plane. To do this i use the follow code: ...
0
votes
0answers
53 views

NSolve or Reduce for obtaining the results and connecting roots

Here I have one problem how to solve numerically equation for different values of one parameter x. I used just two digits because of length, but for x=0.57 I should have one real root and for others ...
8
votes
1answer
214 views

Why does Plot[Hold[x], {x,0,1}] work?

It appears that, counter to my expectation, all of these (and probably many others) seem to work fine: ...
2
votes
2answers
289 views

Converting from TableForm to Grid

I wonder if there is an easy way to convert from TableForm to Grid. I have an existing data format that uses the Table function that I’d like to prettify…. Let’s setup a nested table as follows: ...
2
votes
0answers
71 views

Assign a value to a variable without using Set or SetDelayed?

I supose probably yes, but at the end I assume that internally mathematica has to use Set or SetDelayed. Am I right? Background: I am developing a super simple phraser that takes a code description ...
0
votes
0answers
137 views

Boundary Condition Problem with Green's Function

My temperature distribution looks like: Mean wire temperature is : To[x_] := 2 c1 Cosh[x a1] + a2 And it is continuous at two points. In positive part: ...
2
votes
0answers
104 views

How is Wolfram Language different than regular Mathematica? [duplicate]

From all I can see there seems to be no difference between "Wolfram Language" and regular Mathematica. Is Wolfram just a marketing rebranding of Mathematica or is there a new capability I am missing?
4
votes
1answer
140 views

Import YAML file into Mathematica

Has anyone implemented the import of YAML data files into Mathematica? I suppose some sort of transformation into a nested list of rules would be the way to do it. Thanks
1
vote
1answer
179 views

Plotting a list in real time

I would like to use Mathematica for a presentation and have a list plotted in front of my audience, one coordinate at a time. How would I go about plotting a list progressively in real-time, ie the ...
3
votes
1answer
482 views

Categorical Distribution

Suppose I want to do calculations with a random variable $X$ that has a simple categorical distribution (a.k.a generalised Bernoulli distribution or discrete distribution). I was expecting to be able ...
2
votes
2answers
102 views

Merging two held expressions into a held compound expression

Consider e1 = Hold[a = x + x; b = y + y + y]; e2 = Hold[c = a + a + b + b + b; c^2]; How can I obtain the following? ...
2
votes
1answer
160 views

Order of symbols in Graphics labels

Do you have any idea how to force an order of Greek letter in the graphics? When I type in AxesLabel -> {Cost, Δ OverBar[π]} the order is π Δ. How can I ...
1
vote
1answer
615 views

Why Mathematica can't solve this? NSolve or Solve

I want solution of x and y which should be positive real numbers ...
2
votes
1answer
491 views

2d heat conduction equation: Boundary and initial conditions are inconsistent

I have the following code for a 2d heat c equation: ...
1
vote
0answers
92 views

Define inverse for the custom operator

I want to define simple matrix algebra (inspired by the following posts: Block Matrix Algebra with Mathematica ; How to define custom operators ). I assume the funtion ...
1
vote
1answer
222 views

GatherBy and two conditions

I have a list of 4 dim points, given by ...
1
vote
3answers
229 views

For loop in Mathematica

I have set of statements ...
0
votes
1answer
65 views

Solve equation with two different sets of replacement rules

I want to solve eqn for c0. I want to do it with both replacement rules. I realize I could just use solve twice, once for subsCoke, and once for subsPepsi. I'm trying to do it in just one Sovle to ...
1
vote
0answers
68 views

Problems with manipulating plot in a dialog

G'day, guys. Here is a silly problem I am struggling with. ...
2
votes
1answer
141 views

How to find the zeros of a Complex trigonometric function

I tried this ...
0
votes
0answers
233 views

Shooting method for solving 3rd Oder ODE with RK method

This is my 3rd Order IVP. D[y[x], {x, 3}] == (m/2)*((D[y[x], x])^2 - 1) - ((m + 1)/2)* y*(D[y[x], {x, 2}])^2. Initial conditions given are as follows ...
0
votes
3answers
422 views

Find an equations of motion using Euler Eqution [closed]

I am a completely new to Mathematica, so my question and code may look silly. I need to find a equation of motion of a point particle of mass m moving in a potential V(x) = A abs[x]^n. (n=1,2,3,4,5,6. ...
4
votes
3answers
518 views

Why is my solution to PE #5 so slow

I'm new to Mathematica and it was suggested to me to go through the Project Euler problems in order to learn it. However, I can't quite figure out why my solution to #5 is so slow. The problem: ...
0
votes
1answer
227 views

Why can't Mathematica solve this system of equations?

I am trying to solve the following system of equations for three unknowns Theta, Nu, and K. All the other parameters are constants. The third argument in Solve, ...
1
vote
1answer
117 views

BlockRandom and NestList: how get random maps with the same noise?

I need to compare solutions in random systems with the same noise and different initial conditions. Here I run twice a random map with the same initial condition, inside a ...
1
vote
1answer
65 views

Commutative algebra by generators and quadratic relations

My apologies if this has been asked before. Please also be gentle, as this is my first question here. I am trying to define a commutative algebra by generators and relations in the following way. ...
1
vote
0answers
68 views

Manipulating infinite series

If I type Sum[f[x],{x,m,Infinity}]-Sum[f[x],{x,m+3,Infinity}] I would like Mathematica to return something like ...
3
votes
0answers
322 views

Masked Image Registration/Alignment/Correlation

I'm trying to register (align) two circular grayscale images using a boolean mask to prevent them simply being aligned on the fixed circular border. There are also small fixed circular regions in the ...
0
votes
0answers
46 views

Aborting Multiple Trial Divisions if a Factor is found

I am using Mathematica to perform trial divisions on large Mersenne numbers using specific prime numbers (e.g., primes of the form 8n+1 or 8n-1) and would like the program to abort once a factor is ...
3
votes
1answer
77 views

Complex LogIntegral error

Going through Derbyshire's Prime Obsession & trying to take LogIntegral of 20^ZetaZero[1] & comes up with a value of ...
4
votes
1answer
882 views

NonlinearModelFit does not find a good fit

I am trying to fit my data to the following function, $$\frac{a b t \left(\log \left(\frac{-a d t+a t-1}{a d t}\right)-2\right)}{4 (a t-1)}-c$$ ...
1
vote
0answers
95 views

Increase optimization processing speed

As you know, sometimes numerically solving of optimization problems takes several minutes. For this reason 2 question came up to me: 1 - When one is abort the optimization procedure, how it is ...
4
votes
1answer
75 views

Control Object Annoyance

This may seem like is a trivial annoyance, but it really is a control object "convenience of use" issue. Example: I want to use a popup menu to determine which Excel worksheet I take data from, as ...
1
vote
1answer
480 views

How can you convert a matrix back into a list of lists?

It is very simple in Mathematica to convert a list of lists into a matrix: all you need to do is apply the //MatrixForm function to it and voila. Is it possible ...
6
votes
1answer
147 views

How to inherit options by scoping?

Consider the following example: you have a function framed producing a cell with a button that, when pushed, calls framed again. ...
3
votes
1answer
145 views

How to fill a whole rectangle with text?

I have a rectangle with specified dimensions and I'd like to fill it with text, so that the text uses all (well, as much as possible) of the available area. I tried to do it with ...
2
votes
3answers
325 views

Re-arranging / selecting of a data table very slow in For loop [duplicate]

My task is quite simple; I have a table of data like M = {{1,2}, {1,3}, {3,4}, {5,1}, {6,9}, {6,8}, {6,1}}; so the table is sorted with respect to the first ...
3
votes
1answer
177 views

NDSolve with varying PrecisionGoal and WorkingPrecision

Sometimes we need higher numerical precision to deal with large number cancellation in an equation. But if this cancellation happens only in a small (and known) parameter space, would it be possible ...
4
votes
2answers
176 views

Floating point addition not associative

Can anybody explain the following behavior? x = 0.2 + (0.3 + 0.1); y = (0.2 + 0.3) + 0.1; x == y (* -> True *) But actually the variables do not exactly ...
1
vote
0answers
62 views

Dot shading a.k.a. Stippling effect [duplicate]

I am trying to convert grayscale images to black and white, where I hope to have certain artistic effect, called stippling: I have tried two methods; dithering (with ...
0
votes
1answer
137 views

How to export data in scientific form

I am having an issue about how to export data in its scientific form using Mathematica. To be concrete, I define a list ...
4
votes
1answer
459 views

Testing for OLS Heteroscedasticity White's General Test

I've done my best to search the help and google White's test (http://en.wikipedia.org/wiki/White_test) in Mathematica. Can anyone point me to a function or Mathematica reference for this or do you ...
0
votes
0answers
34 views

Check if a (possibly nested) list is real [duplicate]

I have a very large matrix of numbers. I want to check if all its entries are real. At the moment I am using realQ = And @@ Thread[Flatten[Im @ #] == 0] & Is ...
9
votes
5answers
502 views

Take both of the diagonals through an element in a matrix

I have a matrix like this: Reverse@Array[List, {8, 8}] // MatrixForm I need a function that given an element of this matrix will return all the elements ...

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