# What is Octave: Definition and 40 Discussions

In music, an octave (Latin: octavus: eighth) or perfect octave (sometimes called the diapason) is the interval between one musical pitch and another with double its frequency. The octave relationship is a natural phenomenon that has been referred to as the "basic miracle of music", the use of which is "common in most musical systems". The interval between the first and second harmonics of the harmonic series is an octave.
In Western music notation, notes separated by an octave (or multiple octaves) have the same letter name and are of the same pitch class.
To emphasize that it is one of the perfect intervals (including unison, perfect fourth, and perfect fifth), the octave is designated P8. Other interval qualities are also possible, though rare. The octave above or below an indicated note is sometimes abbreviated 8a or 8va (Italian: all'ottava), 8va bassa (Italian: all'ottava bassa, sometimes also 8vb), or simply 8 for the octave in the direction indicated by placing this mark above or below the staff.

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1. ### MHB When to use equivalence relations? How to write it in octave?

Sometimes to help describe one expression, another expression is shown that produces identical results. The exact equivalence of expressions is indicated with ‘ ≡’. For example: rot90 ([1, 2; 3, 4], -1) ≡ rot90 ([1, 2; 3, 4], 3) ≡ rot90 ([1, 2; 3, 4], 7) What is the meaning of 'rot90;? What...
2. ### Maple GNUPLOT 'file1.dat 2nd column' vs 'file2.dat 1st column'

How can I plot 'file1.dat 2nd column' vs 'file2.dat 1st column' in Gnuplot? If someone can help me with what code I need to write to do it, it will be very helpful.
3. ### Comp Sci Octave coding -- solving a quadratic equation and then using the roots

Hi , I had to solve a quadratic equation , i got two roots as an answer ( ans= x1 / x2) , and now i need to use one of those answers to complete further tasks like finding y from x+y=c so i need to use x1 and x2 from roots , i was wondering if that's possible and how

Hi, I used to use MATLAB for this kind of thing, but now my pc broke and I need to run some scripts. I have a .txt file structured like this 10 -2.34454 12 -2.34566 14 -2.34677 ... ... and I want to store the data in two variables: the first is the "counting" (10, 12, ...) and the second is...
5. ### Structuring Code for Global Parameters in Octave

I'm trying to do a fairly complete system analysis script in Octave that involves these steps: 1) Assign values to all fixed system parameters 2) Make various preliminary calculations based on system parameters 3) Solve a system of differential equations 4) Make various post-ODE solution...
6. ### Structure of code for ODE solution in Octave

The problem of interest at the moment is the solution of a simple damped oscillator problem, xddot+2*zeta*wn*xdot+wn^2*x = 0 Everything seems to work fine provided I include the values of zeta and wn inside the function that defines the derivative values. But zeta and wn are actually calculated...
7. ### Difficulties solving ODE in Octave

I'm new to using Octave 5.1.0, and a bit confused about how to solve ODEs with Octave. Let me show you a bit of code that I grabbed off a university web site: >> function xdot = pend(x,t) % pend.m xdot(1) = x(2); xdot(2) = - x(1) - 0.1*x(2); end >> sol=lsode( "pend",[0.1, 0.2], t =...
8. ### MATLAB Forcing the best fit line to pass through a certain point (Octave)

I have the following code in Octave: h = [29.3 25.3 19.7 16.0 10.9]; v = [0.53 0.47 0.37 0.29 0.21]; plot(h,v,'obk') hold on p = polyfit(h,v,1); y = polyval(p,h); plot(h,y,'-bk') And I get a good graph: I can extrapolate the best fit line using the following code: x = -1:0.01:11; >> y =...
9. ### Need to change display colors in Octave 5.1

I'm running Octave 5.1 on a Win10 system. I find the white background for the editor has far too much glare for old eyes. The orange text used in the editor does not have good contrast with the white background. I could go on, but I'm sure you can see where I want to go. Does anyone know how to...
10. ### A How to find the Jordan Canonical Form of a 5x5 matrix and its steps?

To see the steps I have completed so far, https://math.stackexchange.com/q/3168898/261956 I think there are at least three more steps. The next step is finding the eigenvectors together with the generalized eigenvectors of each eigenvalue. Then we use this to construct the transition matrix...
11. ### Music Understanding Music's Irregular Octave Divisions

One octave is a doubling of frequency, say, 440Hz to 880Hz for A. If I understand correctly, that is divided into 12 equal divisions, denoted by all 12 naturals and sharps/flats. Of those 12, any given key tends to use only 8. Why do these 8, which are not evenly distributed throughout the...
12. ### A Calculate Third Octave Band Response from Narrowband Data

I have a signal that I am able to calculate through an acoustic model for airfoil noise. I am told that the model solves for a narrowband frequency response, however, my measurement data is provided in third-octave band representation. How do I convert my current dataset to the third octave...
13. ### MATLAB Octave integral computation help

Hello, I'm having some trouble with my octave coding and would appreciate any input on where the issue lies. The coding is as follows: age = [0:1:100]; %this is the age matrix, represented by a time = [0:1:100]; %this is the time matrix...
14. ### Calculating Heat Loss in Long Pipe Transfer with Octave

Homework Statement Hello everyone, I hope that you guys could lend me a hand. I need to calculate the heat loss at any point over a long pipe while considering lambda of the pipe. I am trying to use octave to find a reasonable flow-rate to keep the temperature loss to a minimum at a reasonable...
15. ### Am i being taught programming right?

I'm an 2nd year student aiming for the major "Geophysics", my course, "Numerical Programming for Geophysicists" is teaching me how to use Octave, not Matlab, and they force me to use the terminal, not the GUI, on top of that we use Linux, i am also learning Shell and Python. Regarding the...
16. ### Magnetic field representation in Octave

Homework Statement I need to represent in Octave (using the quiver function) the magnetic field lines around a long wire which carries an electric current around the wire. The magnetic field of an infinitely long straight wire can be obtained by applying Ampere's law.Homework Equations The...
17. ### Octave debug info randomly displayed

Okay, I'm not sure if one of the Octave settings got messed up or something, but all of a sudden, in the middle of my run, the Octave console displays a message and all of the debug commands, but doesn't throw an error: 'debug' is a function from the file C:\[path to debug.m] -- Function...
18. ### Can Vector Loops Simplify Theo Jansen's Linkage Mechanism Equations?

I'm studying the work of Theo Jansen and want to derive a set of general equations for motion, velocity and acceleration at each point of his linkage mechanism. I've read a general equation can be derived through the use of vector loops but I am having some trouble as my equations have 10...
19. ### I plotting some data using octave

Hi, I'm having a lot of trouble finding a tutorial that would allow me to plot a set of data using octave. Everything seems to be teaching me how to plot functions. but say I have a list of data saved in a text file. How do I turn this into an xy scatter? Is this possible using octave? I...
20. ### Help with Octave for system of ODEs

Hi, I am having a lot of trouble with Octave as I try to solve a system of ODEs. Any help is appreciated, I am a complete newbie with Octave and numerical solving. Let's try a very simple one. Suppose I had a pair of ODEs with a and b being functions of time \frac{da}{dt}=2ba...
21. ### Octave partial fraction decomposition help

So I'm trying to figure out how to decompose the following using octave: 85000/[(s^2+250^2)(0.2s^2+40s+10000)] I tried using the residue command but I think that only works if the polynomials have real roots, which these don't. When I do use residue I get the following: b =...
22. ### Searching for Octave Bugs - Need Help?

Hello guys, I am familiar with Matlab. And i know Octave is similar to Matlab. I am planning to fix a bug in Octave. Therefore, i would like to ask if anyone know about any bug in Octave (there must be many) or where can i find more information about the same? Thanks!
23. ### Octave with C++ on Fedora 16 | Finding oct.h

Hi all, I'm using Fedora 16 and installed Octave thru Yum. There is an example in the Octave manual of using Octave with C++ and it #includes a oct.h file. However, the Fedora build may not have compiled the oct.h library ? or I'm searching in the wrong places. Has anyone had any...
24. ### Third octave filter and voltage obtained

Homework Statement Hello! Problem is as follows: during measurements laboratory we examined characteristics of a third octave and 10% filters, we were noting down two values at each step --> frequency (ranging from ~1000 to ~1600 Hz) and corresponding voltage. However, in order to read the...
25. ### How to Apply Fourier Analysis with Octave for Signal Transfer Functions?

Hey everyone, So what I'm trying to do is to find the outgoing signal in function of the time, when the transfer function of the filter is known and the incoming signal is a periodic piecewise function. The incoming signal I(t)= 0 for -T/2<t<-T/4...
26. ### LaTeX Software/Tools for Undergraduate Research: R, Octave, Latex & More

I am not sure whether I have posted in the right section. As the title says, I want to know which software/technology I need to be familiar with for making a research paper. I am planning to take an undergraduate research program in my university. It is required for us to make a report in...
27. ### Solving a differential equation numerically (in Octave, Matlab &c.)

Homework Statement I have a second-order non-linear differential equation that I am trying to solve. So far I have decomposed it into a system of 2 first-order equations, and have (possibly) determined that it cannot be solved analytically. So I am trying to do a nice numerical approximation...
28. ### Verifying the Interval of a Fifth vs an Octave in Early Greek Music

Problem (in my words): So, in music, the interval of an octave between two tones corresponds to doubling the frequency of the oscillation. In early Greek music, the interval of a fifth corresponded to multiplying the frequency by 3/2. With this definition of a fifth, prove that non of the...
29. ### MATLAB Running MATLAB Programs in Octave

Hello to all I downloaded Octave. I read that it will run MATLAB programs, but how do you do that? Thanks
30. ### What initial conditions should I use for my system of differential equations?

Hi, I've just started using Octave and I'd like to use it to solve and plot a system of differential equations, but I keep getting the same error which I don't understand. What have I done wrong in my code? Outline: Initial conditions x1 = 1 x2 = 1.27 x 10^-6 x3 = 0 t = 0 - 140 days...
31. ### Octave: Help with implementing midpoint rule

I got the code from my textbook and it is supposed to work in matlab function r = midpoint(a,b,f,n) f = fcnchk(f); h = (b-a)/n; x = (a+h*0.5):h:(b-h*0.5); y = feval(f,x); r = h*sum(y(1:n)); The code fails on feval I go tcnchk from wikipedia function f=fcnchk(x, n) f = x; end...
32. ### How can I display Greek letters in legends using Octave plot?

Homework Statement Hi! I'm sorry if this is misplaced, but I didn't know where else to post it. In my thesis I need greek letters to appear in a legend for a figure generated with octave. Now I normally know how to do that. F.e. if I say: legend('\alpha','\kappa') everythging works...
33. ### MATLAB Octave vs Matlab: Will I Run Into Trouble?

Has anyone here used the open source Octave as opposed to Matlab? I don't have access to Matlab right now and Octave claims to be compatible to a high extent. Will I run into trouble if I learn Octave thoroughly then have to switch to Matlab for collaborative reasons?
34. ### Finding a Cannon Problem to Solve with GNU Octave

Hi to all! My teacher told me to find a problem from the internet based on Cannon throwing a ball, and then to try to solve it using gnu octave. My problem is that I didnt find any problem with cannon. Can you please tell me where to find? Best Regards
35. ### Help with Octave, installing package

Hey, I need some help with installing a package in Octave. I have never done this before so I'm not sure what I am doing wronge. I have downloaded econometrics, changed directory and typed: "pkg install econometrics-1.0.7.tar.gz" and I get """warning: implicit conversion from matrix to string...
36. ### Solid State Physics - Octave (programming) help

I'm currently undertaking a course in Solid State Physics and my professor has asked us to undertake some work in the free software 'Octave'. I have not had any programming experience in my life and I am feeling very much out of my depth. The lecturer gave us an initial file with the relevant...
37. ### Octave programming - some advice for newbie

Hi there - I am looking to get some help in programming with Octave. Trying to work out a random integer generator and well not really getting anywhere so far - I'm hoping someone can give an example or guide in terms of how I should go about doing it in Octave. Thanks