Questions tagged [octave]

Octave is a scientific programming & scripting language with syntax similar to MATLAB and SCILAB.

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23
votes
12answers
19k 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 ...
18
votes
3answers
29k 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 <...
12
votes
3answers
15k 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....
12
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2answers
11k 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 ...
8
votes
3answers
4k 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 ...
7
votes
3answers
220 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 ...
5
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 ...
3
votes
2answers
4k 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 ...
3
votes
1answer
307 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 ...
3
votes
1answer
638 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 ...
3
votes
2answers
4k 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 - ...
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 ...
2
votes
1answer
351 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 ...
2
votes
1answer
659 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 ...
2
votes
2answers
187 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: ...
2
votes
1answer
669 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 ...
2
votes
0answers
74 views

Unforeseen behaviour of fix() in Octave and Scilab

I encountered some odd results when using the function fix() in Octave and Scilab. The following is input and output of the Scilab console but the exact same thing happens in Octave. I start with the ...
1
vote
1answer
47 views

Bode diagram without bode() function

Is there any way to make a bode plot without using the MATLAB/GNU Octave function bode()? As an example, here is a function I am working on: $$H(s) = \frac{1}{2s^...
1
vote
2answers
175 views

How to vectorize 2 nested for loop with one complex condition in the inner loop?

Octave calculations is too slow specially when you deal with scientific calculations that can span a very very large matrix, even just iterating. I have to vectorize it to speed up the calculation. ...
1
vote
2answers
58 views

denoting a variable as a matrix using octave syms package

I'd like to use the syms package to do some algebra for me, but the baseline assumption seems to be that variables are scalars. I would like to denote some variables as matrices. This will change the ...
1
vote
1answer
544 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
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? ...
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. ...
1
vote
1answer
2k 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, ...
1
vote
0answers
67 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
1answer
126 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
vote
0answers
54 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 ...
1
vote
0answers
227 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 ...
0
votes
1answer
213 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. ...
0
votes
2answers
108 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 ...
0
votes
1answer
64 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]; ...
0
votes
1answer
84 views

Minimizing vector norm without using symbolic packages

I am new to octave and still learning what I can and cannot do with it. I am asked to write a following function ('trigmin'): [a, b, c, info]=tigmin(x,y) Where x, ...
0
votes
1answer
88 views

How to write in paper the equations given by splinefit?

I am trying to write on paper the piecewise polynomials given by the splinefit function, but I am having some problems figuring out what the coefficients should be. ...
0
votes
1answer
2k 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 ...
0
votes
1answer
280 views

quiver3 gives non-conformant arguments?

Does anyone know why I'm seeing these errors? I'm not giving it a matrix. ...
-1
votes
1answer
24 views

surface: rows (Z) must be the same as length (Y) and columns (Z) must be the same as length (X) in octave

I am having a dataset and trying to plot a 3-d plot between the independent and dependent variables.but, I am getting this error whenever I am trying to plot here is my code: ...
-1
votes
1answer
20 views

Plot sinewave on ZX axis [duplicate]

I am trying to plot a sinewave with a bit of 3d perspective along the ZX axis instead of the XY axis. I have so far been unable to get anything that works, and have been unable to locate any examples....