# Questions tagged [octave]

For mathematical questions about Octave; questions purely about the language, syntax, or runtime errors would likely be better received on Stack Overflow. Octave is a high-level interpreted language for numerical computations. Use either the (octave) tag or the (matlab) tag, unless your question involves both packages.

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### compute direction of field lines in space of the following vectorfields

i have a hard time to break down these equations and sketch the vector fields. I dont know much math but i really want to solve these and plot them in Octave or Matlab. These quastions are from an ...
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### System identification of a resonant system

I want to write a matlab script that would identify a system from it's inputs and outputs. I have so far had good results with simple systems, but with this slightly more complex one I'm not able to ...
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### Linear Algebra: Residual $A x - b$

I'm doing a course on Applied Linear Algebra. Which, for the most part, is about applications in Octave, so there isn't much about the happenings behind a lot of the mechanics of everything. I'm ...
1 vote
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### Why does the multiplication in a division algebra depends on every component?

In a division algebra A over $\mathbb{R}$ we have this multiplication (A isomorphic to $\mathbb{R}^{n}$) $$\mathbb{R}^{n} \times \mathbb{R}^{n} \to \mathbb{R}^{n}:(x,y)\mapsto y=x\cdot y$$ where every ...
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### Error calculating diffusion equation solution by fft

I''m trying to compute the solutions of: $$\partial_tu=\partial_{xx}u$$ with $x\in[0,1]$ and initial conditions$$u(0,x)=sin(\pi x)$$ Solution are periodic. We have to apply forward euler in time and ...
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### Octave tf2ss: no way to build a system with multiple outputs?

The function in octave tf2ss is supposed to build a state space representation of a system. What I don't understand is how to make it produce a system that has a NxN C matrix, ie a system that outputs ...
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### Conversion from state space back to transfer function in octave.

I'm having problem converting a transfer function to state space and then going back to the same transfer function. I did a little experiment: ...
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### What does adding between dimensions mean if anything at all? Are there useful conventions for doing so? [closed]

Conceptually, why is adding a scalar to a matrix defined ins some cases when adding matrices of different dimensions does not seem to make sense? What does it mean to add a dot to a line, or a line ...
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### Find solutions for multivariable mutliplicative group equation

I have put the following into wolframalpha.com $$11 \equiv x* \left(y^{119}\right)^{149} \pmod{151}$$ It is giving me a set of solutions back. Is it just iterating over all the values of x and y,...
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### DFT implementation: relationship between number of samples and resolution of frequency

I come from an engineer background and I am sorry that this got so long. If $f(t)$ is a continuous signal, let $f[k]$ be the discretized signal for a timerange $T$ between two samples with for ...
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### Calculating correct slope for pitch shifting given starting resonance frequency and ending frequency

How can I calculate the correct slope for variable fac (which controls how much a signal is gradually pitch shifted), if I wanted to end at a certain frequency? An ...
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I have to calculate mod$(2^{1000-k},8k+1)$ (k≤50)with octave. How can I do that? $2^{1000}$ is too big... I think I can split the modulo operation but the code becomes heavy. Is there a way to set ...