Questions tagged [octave]
Octave is a scientific programming & scripting language with syntax similar to MATLAB and SCILAB.
44
questions
0
votes
0
answers
111
views
How to implement large rotations in total lagrangian formulation (nonlinear FEM)?
I have developed an Octave script to solve the nonlinear Euler-Bernoulli beam equations with linearized von Karman-strains, i.e. higher-order terms are dropped. The simulation results agree with ...
- 21
3
votes
1
answer
196
views
How can I extract the banded or block diagonal part of a sparse matrix in MATLAB?
Given a large sparse (square) matrix in MATLAB, how can I extract the banded or the block-diagonal parts (of fixed size) of it efficiently?
These are useful operations when prototyping and testing ...
- 2,301
0
votes
1
answer
305
views
GNU Octave: using 'parallel' with an array (apply function to each array member)
I am new to GNU Octave 6.2.0 on Linux, and I am trying to use the package 'parallel' to make use of 24 threads on my machine.
I have an array (array1) that has ...
0
votes
1
answer
88
views
Rem function in Octave showing wrong result
I am trying to write an if statement that checks if 2 numbers are divisible before running some commands. The problem is, the rem function is giving some wrong results for certain number (2 is ...
- 11
2
votes
2
answers
235
views
(Lack of) Availability of Finite-Difference library for simple 2D PDEs
I would like to solve two types of simple 2D problems, namely the stationary heat equation on an L shaped geometry like this:
And also compute the magnetostactic field in an air gap of the following ...
- 510
0
votes
1
answer
39
views
Plotting two data sets in Octave
I have two data vectors $y1$ and $y2$, and I want to plot both of them as functions of the vector $x$. I want the result to be two overlapping curves. Here is the set of commands I am using.
y2=[0.003,...
- 101
1
vote
1
answer
792
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^...
user36293
0
votes
1
answer
350
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:
...
- 11
0
votes
1
answer
91
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, ...
- 101
1
vote
2
answers
249
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.
...
- 113
2
votes
0
answers
75
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
votes
1
answer
24
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....
1
vote
2
answers
131
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 ...
- 113
0
votes
1
answer
112
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. ...
- 261
0
votes
2
answers
153
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} )$$
The intended result is:
However, using the following ...
- 125
6
votes
1
answer
1k
views
Finite difference method basic implementation on Octave
Trying to study the error of FDM for a second order derivative versus step size I calculated the coefficients and validated them, but the output has errors for small step sizes.
The function in ...
0
votes
1
answer
67
views
Matlab struct vector
(I resume my question with a simple example)
I want to create a struct in matlab/octave as follows
c(1).x = [0 1];
c(2).x = [0 1];
...
c(100).x = [0 1];
...
- 503
1
vote
1
answer
705
views
Plot 2D piecewise constant in matlab in a finite elements mesh
I need to generate a discontinuous plot (piecewise in each triangle) in matlab, something like:
This plot is from http://www.alecjacobson.com/weblog/?p=3616, but I don't understand how generate it.
...
- 503
1
vote
0
answers
73
views
Is MATLAB feasible for app deployment versus lower level languages [duplicate]
MATLAB/Octave is a pretty useful language for prototyping scientific computation use cases, however I would like to know if the sheer nature of being a high level language bottlenecks how fast the ...
- 111
3
votes
2
answers
6k
views
BLAS libraries for Octave or Matlab, preferrably with GPU support?
I just searched around a bit for BLAS implementations and was amazed by the sheer amount of libraries around. Does someone know of a benchmark or otherwise rating of the various libraries?
How easy ...
- 360
0
votes
1
answer
3k
views
Solving Time dependent Schrodinger equation using MATLAB ode45 [closed]
The Schrodinger equation for time-dependent Hamiltonian is
$$i\hbar\frac{d}{dt}\psi(t) = H(t)\psi(t) \, .$$
I try to implement solve the Schrodinger equation for time-dependent Hamiltonian in ODE ...
- 179
2
votes
1
answer
990
views
Defining Cauchy principal value in MATLAB (or Scilab/Maple)?
How to define a variable which is an integral involving cauchy principal value inside in any computer programming language? I want to know how to break down the procedure step by step from a ...
- 179
3
votes
1
answer
383
views
Computational time not proportional to integration interval in ODE-solver?
I am running octave and i have been trying ode45, ode54, ode23 etc to integrate the equation `
$$Q''(t) = B\cos(Q)\sin(\omega t)$$
$$Q(t=0)=0.$$ When the time interval to be integrated increases, the ...
- 153
0
votes
1
answer
257
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
1
answer
131
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 ...
- 111
1
vote
0
answers
55
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
1
answer
741
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 ...
- 297
1
vote
1
answer
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, ...
- 111
14
votes
3
answers
18k
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....
- 255
3
votes
1
answer
2k
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
0
answers
238
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 ...
- 11
2
votes
2
answers
192
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:
...
- 121
1
vote
2
answers
4k
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?
...
- 133
0
votes
1
answer
314
views
quiver3 gives non-conformant arguments?
Does anyone know why I'm seeing these errors? I'm not giving it a matrix.
...
- 101
19
votes
3
answers
33k
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 <...
- 301
1
vote
1
answer
2k
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. ...
- 515
3
votes
2
answers
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 - ...
- 49
8
votes
3
answers
5k
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 ...
- 223
5
votes
1
answer
4k
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 ...
- 153
4
votes
1
answer
2k
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
...
- 1,135
2
votes
1
answer
416
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 ...
- 121
7
votes
3
answers
246
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 ...
- 233
12
votes
2
answers
12k
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 ...
- 221
24
votes
12
answers
20k
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 ...
