All Questions

230 views

Select certain items from nested list

I have a list as follows: lis1={{{a1,b1,c1,d1,e1},{a2,b2,c2,d2,e2}}, {{a3,b3,c3,d3,e3},{a4,b4,c4,d4,e4}}} and would like to delete certain elements from it resp. ...
60 views

Creating separate graphics

I am using the command lines: data = Import["file*.txt", "CSV"] ListLinePlot[data] to plot lists of points. As you can notice, my file name is ...
162 views

FEM in Mathematica and AceGen [closed]

I just wanted to ask, if anybody has already worked with AceGen AceGen, Wolfram Research AceGen, Homepage and knows what clear advantages AceGen has compared to the new FEM in Mathematica 10 ...
70 views

Interpreting Mathematica output or producing cleaner output

Could someone please explain what the following would look like in standard math notation (or explain to me what this means): ...
74 views

How can I use private variables in different ways

How can I use some private variables/symbols in another sub contexts in different ways. Note: Please do not use code Cell Style for testing the codes. ...
112 views

differential equation of order2

I want to solve the following differential equation ode = x*y''[x] + y'[x] + 4*x^2*(x^2 - 1) y[x] == 0 But do not know how to actually solve it. Any suggestion?
131 views

Notebook vs. Kernel: Kernel giving inaccurate results

I am running a code on Mathematica (on Mac OS X) that takes high values for some of the variables. In Notebook, I set the global precision using the following code (which is well documented!) at the ...
439 views

Plotting points from file

How can I plot points (for example {{1 , 1}, {3 , 7}, {5 , 5}}) having as an input a file which contains the points coordinates ? And is there any way to draw a ...
189 views

Video stabilization: extracting the transformation rules used by ImageAlign

Imagine that I have a real life video, with all the artefacts coming from real life, and also from video compression, etc, and that I can edit this video, with filters and cropping, in such a way that ...
90 views

Manipulation of .csv imported data — no blanks in either of two lists

Above is a .csv file. I am trying to construct two lists of male and female math test scores such that only districts which include info for both male and female students are included i.e. neither ...
227 views

Calculate the total length of line segments within polygon

So we have a polygon with N vertices located on grid. All vertices are located at the intersection of cells (so their coordinates are integers). The objective is to calculate the total length of line ...
117 views

Computing a recurrence table backward

I am trying to understand how to compute a recursive equation backward say n = 10 to n = 1. I am trying to solve a PDE for which ...
56 views

Undesired resizing with ImageMultiply and Masking

I want to systematically measure image intensity around each of the points in this 256x256 image. i0: I already have centroid locating code to figure out the centers of each of these points. To ...
85 views

Take sublist with fixed interval

For example: a = Range[20]; a = ArrayReshape[a, {4, 5}] I want to take elements from a with interval = 2 : ...
78 views

NIntegrate producing SetDelayed::write message [closed]

I used NIntegrate to calculate an integral with the final limit as a variable, which later will be listed in a table, ...
146 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 ...
239 views

ParametricPlot3D of Boy's surface

I'm trying to visualize Boy's surface using Bryant's parametrization, as per the MathWorld article. However, I'm not sure I understand the parametrization, and I don't know how to implement it when ...
127 views

How to define $\operatorname{Mc}$ and $\operatorname{Ms}$ Mathieu functions in terms of MathieuC and MathieuS?

Reading multiple books about Mathieu functions, I always come across notation like $\operatorname{ce}_r(z,q)$, $\operatorname{se}_r(z,q)$ for angular functions and $\operatorname{Ce}_r(z,q)$, ...
349 views

Animation of a plane wave

I want to animate in 3D the plane wave $\sin(\omega t+kx+\phi)$, but following the form from the documentation, I can only make $k$ or $\omega$ vary, and I want $t$ to change. How do I do that?
103 views

Second derivative of SmoothKernelDistribution PDF?

Does anyone know why I can't seem to get a second derivative of this interpolating function f? In this example, h[x] is zero ...
155 views

Gridding in a Nested Matrix

We have a nested matrix as: nested={{he, {{e, f, g, h}, {s, 0, q, i}, {s, 0, q, j}}}, {ho, {{e, f, g, h}, {0, u, t, i}, {u, t, 0, j}}}} and with the line ...
105 views

Is it possible to return a list of variable values set by Manipulate?

Is it possible to write a function that returns a set of values that are set by Manipulate? For example, a function that returns a dataset of variables modified by ...
82 views

How can I correct error message that appears each time I launch Mathematica?

Each time I launch Mathematica I get the following error message : The specified setting for the option Magnification cannot be used. I have gone to the option inspector and have confirmed that the ...
346 views

Usage of Piecewise/RSolve to solve an equation based on condition

I am trying to compute price of call option on a stock using the finite difference method. I have a VBA code for it, and I am trying to find out how I can use Mathematica memoization functions and ...
84 views

DifferentialRoot

I want to obtain y(x) of following answer with Mathematica: and my code is ...
278 views

Solve system of equations with implicit function [closed]

I am trying to solve a system of 3 (non-linear) equations with two variables $x,\ y$ and one unknown function $f(x,y)$ of these two variables. Also, the system includes the change of this function $f$ ...
164 views

Generate a list with random values between a and b [closed]

I am trying to perform system identification.. To properly identify the system i have to give the system a "rich" signal which are able to "activate" all the modes of the plant. A rich signal would ...
105 views

Evaluate notebook using text-based interface

I am trying to evaluate a notebook using a text based interface so that it can be submitted to a computing cluster. I have seen this stackexchange page and attempted to use ...
112 views

Memory used by SparseArray objects

In dealing with a quantum mechanics problem, I am representing some many-body states in two different ways in Mathematica. For two parameters n and ...
94 views

Recursive computation using Piecewise

I am trying to create an array using a series of equations using Piecewise. I am stuck in one of them. I am just putting a simplified version of code as below. I ...
71 views

Inequality involving Quantity stays unevaluated

Bug introduced in V10.1 and presisting through V10.4 An expression like this one a < x < b is represented as ...
97 views

Average list of list of parameter values [duplicate]

I have a list of lists of fitted parameter values, e.g. list={{a->1,b->10},{a->2,b->20},{a->3,b->30}} (the actual parameter names can vary, as ...
83 views

Table of ParametricPlots crashes Kernel

I can usually crash the Mathematica Kernel by using Table to generate a List of ...
43 views

How to output matfiles in Mathematica?

I am new to Mathematica, if there is anything wrong, do not hesitate to tell me? ...
141 views

How to do linear fit for 2D data points [closed]

I am very much new to Mathematica, and facing several difficulties. I used the following code Fit[{2, 4, 6, 8}, {1, x}, x] The output is ...
1k views

Solving and Animating Three Body Problem

I am attempting to solve a three-body problem using the Lagrange formalism, with a 1/r potential. I started off by defining T and U (kinetic and potential energy) as follows: ...
61 views

Solve system of differential equations and show the chaotic behavior of the solutions [closed]

I want to solve a system of differential equations and show the chaotic behavior of the solutions. Here x[t], y[t] and ...
86 views

How to get all the symbols x for which f[x] is defined?

Assume that definitions like the following are in place: ...
122 views

Computing a Gamma function-Gaussian integral

I would like to compute the following function: Integrate[Gamma[k,0,Exp[-2 e x^2]],x] k is an integer and ...
145 views

How can I use NonlinearModelFit with multiple variables? [closed]

I am trying to find the coefficients for following equation: $\quad \quad f(x,\,y,\,z) = a (x^2)\, exp(b x + y^2) + c z^2 y$ using NonlinearModelFit. But I can't ...
201 views

Find the volume of the region defined by $|x|+|y|+|z|<4$

I want to find the volume of the region defined by the following inequality: $\quad \quad |x|+|y|+|z|<4$ In addition to calculating the volume of this region, I would also like to be able to ...
136 views

Getting a list of x coordinates of intersection points of two functions

I have two functions, f[x_] := 5 Sin[2 x] g[x_] := (5 x + 2)/(x + 2) I am trying to find the x coordinates that intersect ...
163 views

Specific excel data needed in a list

I need to create a list from a general Excel database that requires only data from "ALL STUDENTS" rows on columns 2 and 7. The List most be of the form {DISTRICT, MATH} where the MATH score is ...
89 views

Arrowhead becomes unattached to line in a Graphics3D Manipulate

I'm trying to Manipulate a Graphics3D figure, and am seeing some errors. If I execute the following code, and move the slider, ...
95 views

Is it possible to sum the results of a Map - Apply?

I am fairly new to functional programming and would like to replace a For[] loop that sums the results over a Dataset. This may be a bit different since the ...
171 views

Inverse Laplace Transform difficulty

I am asked to find the inverse Laplace transform of: $$F(s)=\frac{2s^2+s+13}{(s-1)((s+1)^2+4)}$$ I did the partial fraction decomposition by hand and got: $$F(s)=\frac{2}{s-1}-\frac{3}{(s+1)^2+4}$$ ...
347 views

I don't want Erf[x]

I would much rather have the expression remain as an integral rather than have Mathematica convert it into $\mathrm{erf}$. Is this possible? I always end up differentiating the $\mathrm{erf}$ ...
203 views

How can one plot percentage chart of continuous functions?

I know you can plot percentages using stacked histograms like this: ...