4
votes
5answers
265 views

Can I generate a “piecewise” list from a list in a fast and elegant way?

Suppose we have a number list a: n = 1000000; a = RandomReal[{0, 1}, {n}]; We want to generate a list ...
2
votes
1answer
153 views

Defining and evaluating new continuous distributions based on Mathematica's distributions

A number of functions operate with Mathematica's set of distributions e.g. Through[{Mean, StandardDeviation, Variance}[UniformDistribution[{umin,umax}]]] which ...
5
votes
1answer
407 views

How to express an expression with only ArcTan and ArcTanh?

I have an expression which is simply (j/k) x^(j/k) LerchPhi[x,1,j/k)] where 0 < j < k. Manually I have been able ...
3
votes
3answers
98 views

Operations on expressions within Hold [duplicate]

I want to convert {Hold[1 + 2], Hold[3 + 4], Hold[5*6]} into Hold[{1 + 2, 3 + 4, 5*6}]. I have tried ...
4
votes
1answer
104 views

How to release $Mathematica$ from the $Pre HoldAllComplete lock

Not sure if posted before, but I'm asking this question from a Mathematica fellow user who tried to load expressions, whose problem soon turned into a prison break game featuring the following code. ...
2
votes
0answers
133 views
4
votes
2answers
153 views

Permutations: selecting reviewers without conflicts of interest

I would like to automate the process of selecting a number of proposal reviewers that fit a conflict of interest criterion. Let's say I have 5 reviewers and 5 applicants from 5 departments. The ...
4
votes
0answers
216 views

Using FindFit to fit nonlinear ODE parameters, subject to a constraint (an inverse problem) [duplicate]

Similar to this post I am finding that constraints tend to make FindFit poor at finding a good fit. However, unlike the previous post, the constraints are required ...
1
vote
0answers
40 views

Matching Root[…] objects with patterns, unexpected hidden argument

I needed to write patterns that could distinguish between arbitrary-function and polynomial forms of Root objects, for example, ...
9
votes
4answers
2k views

Removing empty sets from lists

If I had a list, say, names= {"Andy", "Bob", "Carly", "Sandy", "Jeff", "Tim", "Tom", "Zach"} and I decide to pick a characteristic only a certain of them have, ...
2
votes
0answers
65 views

The “right” way to define a custom Encoding format?

I have implemented an Import|Export format for xz that behaves like gzip and other encoding formats: ...
0
votes
1answer
208 views

How do you find the longest sublist within a nested list

Say, I have a list stuff={{eat,tea,now},{how,did,you,say},{the,cat,ate,was,can},{win,din,sin}} I have a nested list and I want to find the list that has the most ...
2
votes
0answers
110 views

Is it possible to use Gaussian cgs units in $Mathematica$ computations?

I was trying to do computations in Gaussian cgs units, and of course I failed due to dimensional issues. For instance, $q_1 q_2/r$ cannot be converted to $\mathrm{erg}$ since Gaussian system uses ...
1
vote
2answers
1k views

Create simple table with function of column values

I just want to create a simple table: Three input columns, one output column Call the inputs {x,y,z}, each can take values ...
0
votes
1answer
495 views

Change font for the whole notebook

Is there any option Mathematica's preferences to change the font for the whole notebook? I know how to change the font of individual cells.
2
votes
2answers
133 views

Plot: how to have the y-range automatically scale to min-max on the x-range?

I have a long list of {date,value}. I would like to use DateListPlot to plot only a subrange, from date1 to date2, with the range on the y-axis automatically chosen to be between the min and max ...
11
votes
3answers
254 views

How to efficiently find moments of a multinormal distribution?

I have a multinormal distribution with covariance matrix $\sigma$ and zero mean. I want to find moment $$ E[x_1^{r_1}x_2^{r_2}\cdots x_n^{r_n}] =\,? $$ Of course, there is a build-in function ...
0
votes
3answers
398 views

Differential equation of mass spring system with compliant stoppers

I would like to solve numerically the differential equation for the displacement x[t] of a mass m-spring ...
0
votes
1answer
747 views

How to plot a function $\psi(r,\theta,\phi=0)$ in polar coordinates?

I have a function $\psi(r,\theta,\phi=\phi_0)$ with $\phi_0\in \Re$, $r\in[0,R]$ with $R\in \Re$, and $\theta \in [0,\pi]$ (spherical polar coordinates) and I want to plot it in Mathematica. I guess ...
2
votes
1answer
86 views

Export to CDF fails

The code below generates the error when I attempt to export to CDF Preview: Coordinate {xde[4.69588928222656], yde[4.69588928222656]} should be a pair of numbers, or a Scaled or Offset form. ...
5
votes
1answer
117 views

Text formatting with different wrappers

Formatting text in Mathematica should be a punishment for serious crimes. I've face another frustrating feature, and I don't know how to get rid of it. ...
2
votes
1answer
168 views

Mathlink works strangely

I have problem when using mathlink, the source code is quite simple: ...
6
votes
1answer
172 views

The third argument of the Root function

Consider the roots of an arbitrary indecomposable polynomial: sol = Solve[x^5 + 2 x + 1 == 0, x] The returned expression is ...
0
votes
1answer
90 views

Is there any automatic method for rating function arguments importance?

If I have a function: y = 2a + 5b + c It can be easily seen that b is the most important parameter, next ...
6
votes
2answers
622 views

Find parameters of ODEs to fit solution data

Problem How to find the initial conditions x[0],y[0] and the optimal value of parameters ...
0
votes
1answer
139 views

Plotting values above a threshold in ListPlot3D

I'm able to plot a 3D plot of a grayscale image using ListPlot3D, where it plots a 3D surface of the image pixel intensity. But I would like not to plot the pixel ...
1
vote
0answers
131 views

Defining an operator

Let s be a positive integer and let DifferenceDelta be this function with step = 1. Define ...
1
vote
0answers
132 views

NIntegrate doesn't work

I have a function, Dx[s] (defined in a module) which I can plot: Plot[Dx[s], {s, 0, GetLatticeLength[]}] However if I try ...
0
votes
1answer
83 views

Stop function evaluating input at time of definition [duplicate]

I would like to create a function that acts on whether the input is even or odd, e.g.: In[644]:= f[a_] = If[EvenQ[a], 2 a, 3 a]; f[2] Out[645]= 6 I've ...
5
votes
1answer
254 views

What algorithm and tools should I use to search a data set for the point nearest to a given point?

I have about 1,000,000,000 points, which are the longitudes and latitudes of some places in a city, formatted like this: $(106.1231233,41.43234234)$. I also have about 20,000 points which are the ...
5
votes
2answers
191 views

how to improve efficiency when I want to classify a list according to certain laws

I have a function that generates lists: f[n_] := Join @@ Permutations /@ PadLeft@IntegerPartitions[n]; For example f[3] ...
3
votes
2answers
233 views

Generation function of recurrence sequence

I'm trying to find generation function of recurrence sequence ...
2
votes
1answer
138 views

Evaluating Abs'[2 x] gives different results than evaluating D[Abs[2 x], x]

I noticed the following difference Assuming[x ∈ Reals, FullSimplify[D[Abs[2 x], x]]] (* 2 Sign[x] *) Assuming[x ∈ Reals, FullSimplify[Abs'[2 x]]] (* Sign[x] *) ...
5
votes
2answers
253 views

Grid ItemSize is smaller than expected

If I execute MatrixPlot@IdentityMatrix@100, the result is a good size. However, if I evaluate ...
2
votes
2answers
119 views

How do I assign specific data points in an array to a new array?

I am trying to learn how to script/program in mathematica and I am retyping some simple C and FORTRAN programs into Mathematica as a way to learn. I am writing a Monte Carlo code to calculate the ...
6
votes
1answer
340 views

My black text isn't black after exporting to PDF

Consider any standard plot, with true CMYK black text: ...
1
vote
1answer
220 views

Solving an exponential multivariate equation

I have the following equation: p = 1/(1 + E^(-51.179 + 0.849 x1 + 2.3649 x2 + 1.155 x3 + 1.46 x4 + 1.31 x5)) and I want to find the set of values for x1 to x5 ...
0
votes
1answer
442 views

plotting xy, yz, zx plane at

I have a data list in the following form, data = {x, y, z, f} I would like to present three kinds of subdata set as a density (or contour) plot on the ...
8
votes
3answers
267 views

finding anagrams

What I'm trying to find are the 4 letter words in the mathematica dictionary that have the most anagrams and the amount of anagrams these have each. But I can't seem to find all the 4 letter words in ...
0
votes
4answers
44 views

How to multy-Set a group of lists?

I have a group of lists, for example: lists = RandomInteger[10, {100, 2}] {{6, 7}, {7, 4}, {3, 3}, ....} Now, I want to ...
0
votes
1answer
182 views

How to return the rhs of a transformation rule from within Compile[]

I have defined the following function: ...
-1
votes
1answer
78 views

map rational number [duplicate]

I am trying to map this function ((-1)^(1/Denominator[#]))^Numerator[#]==(-1)^#& to a fairly big list of random rational numbers I am trying to get this to ...
2
votes
1answer
83 views

Is it possible to merge cells excluding results with one click?

Now when I merge two cells with right-click "Merge Cells", they merge with the results included, while I only want the commands merged. Can I make it a one-click button? Now I have to delete the ...
0
votes
1answer
89 views

Plot producing many error messages when given complicated function

I'm new to Mathematica and am running in to all sorts of silly difficulties with coding in it. I'm trying to calculate a function f[x, k], normalise it with another ...
4
votes
3answers
355 views

Draw plot with locator & slider

I would like to create a plot whereby both the slider and the locator 'draw' the plot. In the following code, the locator & the slider act independently: ...
5
votes
1answer
247 views

Visualization of iteration procedure in NMinimize

I have this optimization code: ...
8
votes
1answer
128 views

Strange behaviour of Internal`InheritedBlock

I was going to post an answer for fast way to replace all zeros in the matrix. I was even quite happy because timings were the same order of magnitude as others. The idea was to overwrite ...
0
votes
1answer
85 views

What's wrong with my implementation on CountryData

I was wondering, *for which countries is the proportion of Phone line users to population greater than or equal to that of the United States?* This is what I inputted below, but the list of countries ...
9
votes
3answers
16k views

MathLink linking error after OS X 10.9 (Mavericks) upgrade

After macosx 10.9 mavericks upgrade i have a compilation problem, you can see below. Even the examples given in ...
-1
votes
4answers
284 views

Animate a triangle that follows a curve

Given: ...

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