# All Questions

55 views

### How to freeze and test a list of programs?

I have a list of problems for my students and I'm trying to use the new v10 feature TestResults like so: ...
43 views

### Does a matrix need to be rationalized when calculating MatrixExp? [on hold]

I have a sparse matrix, L, and need to calculate its exponential, MatrixExp[L t], where t is ...
52 views

### OLS Estimation - Computational results vs. calculation by hand [on hold]

I calculated the OLS estimators for a data set by hand using $$\hat\beta=(X^TX)^{-1}X^Ty$$ If I check my results with Mathematica I get different results. I'm quite sure that I didn't make any ...
88 views

### Calculation of 2D FFT for an image

I am trying to obtain 2D FFT of an image. From the 2D FFT, I wish to calculate the amplitude of the FFT averaged over a circle vs the distance in pixels by varying the radius of the pixels which is ...
51 views

### Simple ways to implement vector dilation

Suppose we have a singly connected but not necessarily convex polygon. Something like shape = CountryData["Chad", "Coordinates"]. Is there a simple way to ...
35 views

I am trying to solve a system of differential equations. ...
36 views

### Generation of list of values for small gap among values

I need to run a loop as Table[expr,{i,imin,imax,di}] where I want di to be as small as order of ...
56 views

### Export NDSolve results

I can see the correct result of my NDSolve when I plot them with large PlotPoints. ...
50 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 ...
29 views

### problem exporting an Animate video

Here's my code: ...
78 views

### How to solve the following fourth order partial differential equation including Laplacian

I wish to solve the following fourth order partial differential equation including Laplacian with the boundary conditions with the initial conditions ...
29 views

### rgb2ycbcr and ycbcr2rgb performing twice on same image gives different answers? [on hold]

I converted an image from rgb to ycbcr using rgb2ycbcr. Then converted back to rgb using ycbcr2rgb. Again converted the resulting image from rgb2ycbcr. But in the first and second rgb2ycbcr ...
219 views

### Integration of linked PDFs over probability simplex

I'm trying to integrate the following expression: f[a1,p1+p2+p3+p4]*f[a2,p2+p3+p4]*f[a3,p3+p4]*f[a4,p4] Where ...
135 views

### Solving differential equation with initial conditions

I want to solve the following differential equation with initial conditions: ...
90 views

### How to Optimize Solution? (Project Euler #14) [duplicate]

Link to Question: https://projecteuler.net/problem=14 I began by defining the following functions below. ...
8 views

### Mathematical formal expression of find “subfunction” in function [migrated]

Imagine if I have a function $s(t)$ and $r(t)$. $s(t)$ may contain $r(t)$ one or more times as $s(t)$ is a quasi-period function. What is the correct expression if I want to say the $s(t)$ contains ...
73 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 ...
128 views

### Wavelet Transform Modulus Maxima (WTMM) method

Has anyone already coded the Wavelet Transform Modulus Maxima (WTMM) method for computing the singular spectrum using multi fractal formalism in Mathematica? The goal is to analyse 1D, 2D and 3D ...
110 views

### Initializing several values of a function

How do I initialize several values of a function at once? Consider the function f[0] := 1; f[1] := 2; f[2] := 3; f[n_] := f[n] = f[n-1] + f[n-2] + f[n-3]; Is ...
74 views

### How to disable half-hiding output, when the corresponding input cell is modified

I think it has become less easy to compare the new output, now that the output font color turns gray as soon as something is modified in the input cell. Is there any solution?
99 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 ...
33 views

### Creating eigenvalues of a matrix [on hold]

How do I store eigenvalues of a matrix in a For loop into a two dimensional array and then plot that array?
41 views

### Why is the Max function so slow when operating on lists of dates?

Example: dates = DateRange[DateObject[], DatePlus[DateObject[], 15]]; First[AbsoluteTiming[Max[dates]]] (* 21.364247 *) As a workaround, ...
1k views

### How do I obtain the enclosed area of this particular parametric plot?

I'm trying to find a way to obtain the enclosed area of this particular plot. Can someone show me how? ...
49 views

### AppendTo or Part in a ParallelDo?

I have a question regarding how memory is managed in parallel. Specifically, I'd like to know what is the better practice when constructing an array within a ...
152 views

### NonlinearModelFit giving message NonlinearModelFit::nrlnum: [on hold]

I'm trying to fit my data using NonlinearModelFit, but I keep getting errors that I don't quite understand how to correct ...
148 views

### Defining a function implicitly and calculating its derivatives

I'm interested in using Mathematica's symbolic manipulation to obtain, for a particular function $f$, derivatives of arbitrary order evaluated at zero. Normally I'd use the ...
54 views

### NSolve not solving [on hold]

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 ...
578 views

### a problem about simplifing conjugate

the situation is as follows ...
79 views

### FullSimplify not giving me a physically useful answer for Mott scattering

I am using Mathematica to find the cross-section for Mott scattering over an extended target. I evaluated ...
47 views

### Displaying Greek letters with subscripts inside plot [duplicate]

I am using ListPlot: ...
33 views

### exporting 3D graphics in STL format (for 3D printing) [duplicate]

How do I set the size of the exported item? (Graphics3D has no implied unit, so it is not a-priori clear what size the object will be, and experiment indicates that ...
49 views

### A question about the syntax [on hold]

I have $3$ elementary questions to ask and I thank you in advance. Question N°1. What is the right syntax for $$y\equiv0\pmod {2}$$ in the code below? ...
61 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 ...
94 views

### Unexpected results from GARCH Processes

I'm playing a bit with Time Series and I've been trying to estimate Garch Processes from different time series. Are TimeSeriesModelFit and ...
165 views

### Factoring the imaginary unit

Suppose you have this: Collect[2 u + I + 2 + I,I] It gives the same. Is it possible to factor I in elegant way (not ...
158 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 ...
98 views

### Appending elements to a list in parallel table

Is there any way to store values in a list that is being computed in parallel? For example, if ParallelTable is computing some ...
671 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: ...
275 views

### How to use the Testing Notebook to test a package?

I think an important purpose of the new Testing Notebook in version 10 should be to test user packages (instead to test the builtin functions in the ...
186 views

### Problems finding intersection points between line and generic function

I'm trying to find Intersection points between a line, which is given by 2 points, and a generic function (I want it to be able to handle polynomial functions, circles/ovals, lines and all ...
105 views

### Equation involving hypergeometric functions

I want to solve this equation but nor NSolve nor Solve are able to do this. ...
616 views

### Nearest neighbor search in n-dimensions

Suppose a list of items such as: L1 = RandomReal[{0, 100}, 1000]; I need to find the position of each k-neighbor in the original list. And very quickly if ...
138 views

### Using Simplify on a consistent system returns False

Bug introduced in 8.0 and persisting through 10.1.0 or later It's late, but am I missing something here? Why should two independent equations, which together are consistent, ...
65 views

### How to use Wolfram language in an external program with low latency?

Im using Wolfram language on Pi B,and I want to compile a '.m' file (like "test.m" that contains Wolfram functions), in an external program like a C/C++ and then Export the output in an image file ...
93 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 ...
40 views

### Import 3D Jpeg file [on hold]

How can I import 3D jpeg file to Mathematica ? I would like to import it and save it into a 3D pdf format. This is the images
46 views

### Defining A Function With A Certain Domain

I am trying to plot the numerical range a matrix, which is a set defined like so: $W(A) = \{\langle Ax,x \rangle : x \in \mathbb{C}^n \text{ and } ||x|| = 1\}$ In other words, I am trying to plot ...