Questions tagged [octave]
Octave is a scientific programming & scripting language with syntax similar to MATLAB and SCILAB.
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2answers
57 views
Plot a multi-variable equation in (discontinuous) regions
The goal is to display the relation between K and E in the following equation:
$$\cos(K) = 5 \text{sinc}( 5.12\sqrt{E} ) - \cos(5.12\sqrt{E} )$$
The intended result is:
However, using the following ...
3
votes
1answer
277 views
Finite difference method basic implementation on Octave
Trying to study the error of FDM for a second order derivative versus step size I calculated the coefficients and validated them, but the output has errors for small step sizes.
The function in ...
0
votes
1answer
51 views
Matlab struct vector
(I resume my question with a simple example)
I want to create a struct in matlab/octave as follows
c(1).x = [0 1];
c(2).x = [0 1];
...
c(100).x = [0 1];
...
1
vote
1answer
284 views
Plot 2D piecewise constant in matlab in a finite elements mesh
I need to generate a discontinuous plot (piecewise in each triangle) in matlab, something like:
This plot is from http://www.alecjacobson.com/weblog/?p=3616, but I don't understand how generate it.
...
1
vote
0answers
63 views
Is MATLAB feasible for app deployment versus lower level languages [duplicate]
MATLAB/Octave is a pretty useful language for prototyping scientific computation use cases, however I would like to know if the sheer nature of being a high level language bottlenecks how fast the ...
1
vote
2answers
2k views
BLAS libraries for Octave or Matlab, preferrably with GPU support?
I just searched around a bit for BLAS implementations and was amazed by the sheer amount of libraries around. Does someone know of a benchmark or otherwise rating of the various libraries?
How easy ...
0
votes
1answer
985 views
Solving Time dependent Schrodinger equation using MATLAB ode45 [closed]
The Schrodinger equation for time-dependent Hamiltonian is
$$i\hbar\frac{d}{dt}\psi(t) = H(t)\psi(t) \, .$$
I try to implement solve the Schrodinger equation for time-dependent Hamiltonian in ODE ...
3
votes
1answer
395 views
Defining Cauchy principal value in MATLAB (or Scilab/Maple)?
How to define a variable which is an integral involving cauchy principal value inside in any computer programming language? I want to know how to break down the procedure step by step from a ...
3
votes
1answer
267 views
Computational time not proportional to integration interval in ODE-solver?
I am running octave and i have been trying ode45, ode54, ode23 etc to integrate the equation `
$$Q''(t) = B\cos(Q)\sin(\omega t)$$
$$Q(t=0)=0.$$ When the time interval to be integrated increases, the ...
0
votes
1answer
177 views
Nice plot of f(x)
A user has this nice graph of f(x) on his profile and I want to learn how to do it in matlab or Gnu octave.
...
1
vote
1answer
119 views
Applying a weighting function which is sampled at different points
I have a set of data to which I want to apply a weighting function, so basically a simple multiplication.
My sampled data looks like this:
(for those interested, it's the relative luminous intensity ...
1
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0answers
49 views
Software to simulate behavioral economic models?
I am looking for a way to simulate behavioral economic models to illustrate the effects of changing parameters. I am familiar with statistical analysis (especially R), but I only have few programming ...
2
votes
1answer
549 views
eigs routine in octave [closed]
I am using octave and observed a problem with the eigs-routine for non symmetric matrices. Using GNU octave version 3.8.1 the code below gives significant difference of eigenvalues although same ...
1
vote
1answer
1k views
Solve poisson equation with Neumann b.c. (matlab or octave)
I'm trying to reconstruct an image given its Laplacian, which results in a Poisson equation and I'm using Neumann boundary conditions (derivative at boundary = 0).
What I have is the laplacian (f, ...
12
votes
3answers
11k views
Alternatives to Comsol Multiphysics
This might be a question better suited for the Software Recommendations side of S.E., however I do believe that people who frequent this part of S.E. are more likely to be able to answer this question....
3
votes
1answer
1k views
Partial differential equations with octave [closed]
I need to find a numerical solution for $-\Delta U = f$, on the $\Omega = [0,1]^2$, with $ U|_{\partial \Omega} = 0$.
I found a method: POISSONFD in ...
1
vote
0answers
218 views
Printing a plot in Octave-3.8.1 breaks LaTeX labels [closed]
Since upgrading to Octave 3.8 I have been unable to export plots with LaTeX labels. When the figure is displayed the labels render fine but when I try to export the figure using the ...
2
votes
2answers
183 views
Solve chemical formula (number of molecules in reaction)
In order to balance atom count in chemical equation:
a O2 + b C12H24O11 → c CO2 + d H2O
I make linear equation:
...
1
vote
2answers
3k views
Polar axes in Octave?
if i draw a polar plot with Octave the axes are cartessian, not polar axes. But in Matlab it seems polar axes exists for polar plots. Is there anyway to draw with polar axes in polar plots in Octave?
...
0
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1answer
242 views
quiver3 gives non-conformant arguments?
Does anyone know why I'm seeing these errors? I'm not giving it a matrix.
...
14
votes
3answers
21k views
Euclidean distance in Octave
I would like to know if there is a quick way to compute the Euclidean distance of two vectors in Octave. It seems that there is no special function for that, so should I just use the formula with <...
1
vote
1answer
1k views
How can I get Octave to correctly compute a double integral of a piecewise function?
Computational Science People:
The title is the question. I am trying to numerically compute a certain integral over a square in Octave (an open-source Matlab clone). I'm getting the wrong answer. ...
3
votes
2answers
3k views
Octave 3D mesh, data from file
I have a big file with 3 columns: density, dimension, value.
example:
10 0.3 200
10 0.4 300
20 0.3 250
20 0.4 320
...
I am trying to draw a 3d plot - ...
8
votes
3answers
3k views
fmincg implementation in Python
I'm trying to re-implement Neural Networks in Python. I implemented the cost function and the backpropagation algorithm correctly. I have checked them by executing its Octave equivalent code.
But ...
4
votes
1answer
3k views
Plotting x,y coordinates and vectors with octave
I have a data set containing the recorded data from a car's motion (latitude,longitude, and heading). I'd like to plot the (lat,lon) points on a 2D plot with a unit vector pointing in the direction ...
4
votes
1answer
1k views
Python syntax for MATLAB/Octave colon operator a:dx:b
I am trying to rewrite some MATLAB/Octave code in Python, and I don't know what would be the nicest or most intuitive way of writing
...
2
votes
1answer
331 views
In Octave, how do I specify that the solution to a matrix equation should be over integers?
In Octave, how do I specify that the solution to a matrix equation should be over integers?
I.e., Given matrix $A$, vectors $x$ and $b$; $Ax=b$. Find vector $x=A^{-1}b$ such that all its entries are ...
7
votes
3answers
211 views
Converting from planar polynomial domain to planar polygon
Let's assume we have a planar domain whose boundary can be described with a polynomial curve (like Bezier curves).
Now assume that you want to produce a discretization of the boundary, i.e. you want ...
12
votes
2answers
9k views
Octave: calculate distance between two matrices of vectors
Suppose I have two matrices Nx2, Mx2 representing N, M 2d vectors respectively.
Is there a simple and good way to calculate distances between each vector pair (n, m)?
The easy but inefficient way is ...
22
votes
12answers
18k views
Is it possible to use Octave to learn MATLAB programming?
I want to learn MATLAB programming so that I can conduct some researh/analysis on my own and also, so that I can study/modify some MATLAB scripts that I have found online etc.
However, the problem is ...
