0
votes
1answer
51 views

Solving differential equation (Analytical or Numerical)

I want to solve the following differential equation for $0 < x < 1$ ...
0
votes
1answer
58 views

NDSolve Problems with Cardiovascular Modeling [duplicate]

I am trying to use 27 simultaneous differential equations to model the cardiovascular system. I have the following code, however, the output isn't giving interpolating functions, but rather another ...
2
votes
1answer
36 views

SetDirectory[NotebookDirectory[]] in one notebook causes Directory[] to change in a different notebook

This is causing me lots of problems. I found that issuing SetDirectory[NotebookDirectory[]]; in notebook A.nb causes subsequent ...
2
votes
1answer
62 views

Why are these methods giving me different results? (Trying to test SplineFit)

I am creating a polymer(where each monomer is of equal length) using this method: ...
6
votes
3answers
119 views

Evaluate a expression split in a list

I have a list with this format {integer, sign, integer, sign, integer}, sign being one of these: Plus, Subtract, Times, Divide. For example, let's say: ...
3
votes
0answers
100 views

Why is Thread[{ a, b }] the same as Transpose[{ a, b }]?

I understand the idea of both Thread and Transpose, but do not understand whatever nuance it is that makes Thread[{ a, b }] == Transpose[{ a, b }] Where ...
8
votes
2answers
300 views

AJAX-style HTTP calls triggered by a variable change

I'm trying to create a dynamic InputField that would autocomplete the address as I type it into the field, by calling Google Maps' GeoCoding API on every change of ...
0
votes
1answer
46 views

Stopping sliders in Manipulate going to dynamic unfeasible regions

I am trying to use Manipulate to create a function which allows a user to play with a probability density. The following generates a static density over the range 2000 - 4000, then allows the user to ...
-1
votes
1answer
69 views

Coefficient: how to simplify the “form” [closed]

The title is not very clear, but my English is not that good, so I didn't know how else to write it. So, let's get to the problem. I have a list of elements, in form of a sum, like this: $finalstate ...
1
vote
0answers
52 views

Finding the global extrema of a surface? [closed]

I am trying to figure out how to find the global extrema of the function surface shown below and can't seem to get answers that make any sense. I am using the FindMinimum and FindMaximum functions ...
3
votes
3answers
126 views

When using NDsolve, how to determine the positions of steady states?

I am currently trying to numerically solve a set of ordinary differential equations of chemical kinetics. However, I want to implement perturbations only when system reach steady states. For example ...
4
votes
1answer
42 views

How to define a function to save a list to a same-name file

I want a convenient way to save lots of intermediate data lists into files, so that next time the files can be imported automatically to homonym list variables in the notebook, without having to ...
0
votes
1answer
43 views

Bin a large matrix

I have a large dataset and I'm trying to plot its scatterplot as well as an overlayed set of binned "summary" data points (in a different color of course). My intended effect is similar to this one ...
0
votes
0answers
38 views

Stringifying $GeoLocation for the browser

Currently, when I ask for ExportString[{"geoLocation"->TextString[$GeoLocation]},"JSON", "Compact"->True] I get this: ...
2
votes
1answer
113 views

How can I find all solutions of a complicated expression in a desired interval with Mathematica?

I have an expression which is a combination of Bessel functions: ...
14
votes
3answers
612 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 ...
4
votes
1answer
67 views

Query Dataset to check if row contains any from a set of values

For a given keyless dataset, I can query to return the rows whose columns contain a specific value. For example: ...
3
votes
2answers
136 views

Why are dictionary keys reordered upon JSON import?

After importing a JSON file, Mathematica changed the order of the fields. For example, I downloaded a sample file from: http://api.openweathermap.org/data/2.5/find?lat=55.5&lon=37.5&cnt=10 I ...
2
votes
1answer
115 views

Integration doesn't work

I'm trying to obtain the following integral: ...
1
vote
1answer
93 views

Animating a 3D shape along path a (2D and 3D) parametric function curve [Update]

I have a 3D object under the action of gravity field.The trajectory of path is a parabola.I would like to animate , as in the example GIF. ...
0
votes
0answers
47 views

Null space of a stochastic matrix [closed]

I want to calculate NullSpace of a matrix m - IdentityMatrix[n]. Normally I would do it with ...
3
votes
2answers
87 views

Put together two ListLinePlot with right alignment

I would like to ask for some help to figure out how can i put two ListLinePlot together with right alignment. Here is what i tried to do: ...
4
votes
2answers
79 views

Pauli matrices — simplify expressions without printing out the raw matrix

Squaring a Pauli matrix results in the identity matrix. These bits of documentation (weakly, to a Mathematica-newbie like me) imply that some algebraic identities that link the Pauli matrices ...
0
votes
0answers
37 views

How to get this numerical solution of a integro-differential equation [migrated]

Previously, I ask an NDSolve questions(How to solve the differential equation with Duhamel's integral?), but now a more sophisticated one: ...
2
votes
2answers
80 views

Plotting a 2D mapping of a 2 column ASCII

From my SIMS I can export the image mappings in form of a two column ASCII file. For example if it were a 5x5 pixel mapping, it would give something like this: ...
3
votes
2answers
71 views

Plot with special special gridlines [closed]

I would like to plot a function in plane with axes grid-lines labeled as follows, $1,\sqrt{2},\sqrt{3},\sqrt{4},\sqrt{5},\ldots$, instead of the usual 1, 2, 3, 4, 5, ....
0
votes
1answer
36 views

Expression evaluation [closed]

I have got the following solution to an equation: ...
3
votes
1answer
80 views

Solve an eigensystem faster and eliminate Root[…] from the solution

I have a symbolic, 2-parameter, 8x8 matrix to solve, but Mathematica takes something like 20 minutes to solve it and returns a very large output containing expressions of the form ...
4
votes
1answer
56 views

ListLogLinearPlot with customize Mesh mix up the markers in multiple curve

I have to plot several curves in logarithmic scale. I used ListLogLinearPlot and customized the Mesh option. Then the markers mixed up. ...
2
votes
1answer
67 views

Memory usage optimization for a large Association/SparseArray

Reformulating my question in simpler terms. Take two lists list1 = RandomInteger[{1, 100000000}, 25000000]; list2 = RandomReal[{1, 10}, 25000000]; Make an ...
0
votes
0answers
15 views

How to plot `y=y[x]` from `f[x_,y_]=f0` [duplicate]

Given a two-variable function f[x_,y_]:=(*complicated stuff in terms of x and y *) what I want is to do is Plot ...
0
votes
1answer
39 views

How to simplify and evaluate Integral with lots of DiracDelta dists

I have a question about an Integrals which I can do by hand but I want to implement this Integral in Mathematica. Actually it is the definition of a 2 Particle Phase Space. The Expression is the ...
4
votes
1answer
128 views
+50

Confirming conservation laws for complex valued functions

Consider the nonlinear Schrödinger equation (I would like to do this for a more complicated set of equations, but to gain understanding I'll consider this simplified case) $$A_t+iA_{xx}+i|A|^2A =0,$$ ...
0
votes
0answers
105 views

MeshFunction at azimuthal angles for RegionPlot3D

Edit: I said "polar angle"... It should be "Azimuthal angle". Sorry. I want to plot a Mesh line at a certain azimuthal angle in RegionPlot3D. My goal is to ...
2
votes
1answer
42 views

Integrate and NIntegrate combined, giving MaxPrecision error

I am trying to integrate the following : ...
1
vote
1answer
63 views

Can I Adjust Thickness of Spheres and Cylinders to Make Objects Printable in 3D?

I have a design of a crystal structure using Sphere and Cylinder in Mathematica. I then exported the result as an STL file and tried to print it. I was told that the objects were "too thin," that ...
0
votes
0answers
33 views

Why is there a different eigenvector for the same matrix? [duplicate]

I have a matrix that depends on two variables x and y. Matrix[x,y] When I make x=-.25*(1 - 1/3) + .25*(1/3) + .25 y=0 I ...
0
votes
0answers
25 views

Extracting coefficients of very large polynomials (perhaps by improving Expand or ExpandAll)

Is there a way to improve or bypass Expand (or ExpandAll) for extremely large polynomials? I have a polynomial system of the form $$ 0 = \sum_n a_n d_{i_1,i_2} \cdots d_{i_{p-1},i_p},$$ in which ...
7
votes
4answers
225 views

How to iterate over the columns of a Dataset?

I have a Dataset with a simple structure, like this: ...
7
votes
1answer
79 views

What do RecursionLimit and IterationLimit actually set?

The following recursive functions respectively calculate the length of a Short-cut Collatz Conjecture series and perform a pointless demonstration recursion: ...
10
votes
1answer
210 views

How do I create a triangulated surface from points?

I have a set of points in a nx3 matrix and I would like to convert them into a surface, so that I may calculate its surface area. The function ListSurfacePlot3D creates the surface how I want it. ...
0
votes
1answer
31 views

How can one make NDSolve spend less time at irrelevant transient oscillation?

In the solution there is a transient oscillation that is irrelevant. NDSolve spends a lot of time there. Is there a way to optimize it?
2
votes
2answers
78 views

Better to use loop or function when populated list?

In the past I have pretty much stuck to expression building when using Mathematica, but recently I have been writing a procedure to populate an array, which I guess are called "lists" in Mathematica. ...
0
votes
3answers
67 views

Problems with finding the real solutions of equation

I am trying to find real solutions of equation using Mathematica 8.0 but there is some problem I don't know how to explain. For example, for the input ...
21
votes
2answers
1k views

Why do Mathematica list indices start at 1? [closed]

In most programming languages, container indices start at 0. This is not random or hardware-related; for example Dijkstra's article explains why zero-based indices make sense. What are the reasons ...
0
votes
1answer
35 views

Unexpected ReplaceAll behavior with NSolve

I ran into some unexpected behavior using ReplaceAll with an equation of motion using NSolve (or Solve, also). First solving for the initial velocity v0: ...
1
vote
1answer
43 views

Concatenated rule applications (applying rules to rules correctly)

I am trying to apply a series of individual rules onto an expression sequentially, but also not have to write out the repeated ReplaceAll functions each time I want ...
3
votes
2answers
104 views

Matrix Plot: How to Apply color function to only a region of the plot

I want to make a matrix plot where a color function is applied to a region of a matrix. Those matrix elements which were not in the region specified should not have any color associated with them, and ...
5
votes
4answers
253 views

Deleting multiple elements from a list

I have a list with many elements (189) and I want to delete certain elements from it. I have a list of elements I want deleted from it: ...
1
vote
1answer
53 views

Weird sum regularization? [duplicate]

I noticed some weird behavior in "Dirichlet" regularization of infinite sums. Let us first compute ...

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