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Bjorn Gustavsson


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UIT, the Arctic University of Norway

408 total contributions since 2015

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Answered
Pcolor equivalent for 3D array
The type of plot you've presented is easily reproduced by this: [x,y,z] = meshgrid(0:3,0:4,0:5); F = floor(4*rand(size(x))); ...

ungefär 20 timmar ago | 0

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Answered
Pcolor equivalent for 3D array
For visualization of 3-D data matlab has a couple of builtin functions: slice, scatter3 and isosurface. They does tasks at least...

2 dagar ago | 0

Answered
How to create multiple files with given one file name
I'd do something like this: fn = '/some/where/output.csv'; [pth,nmn,ext] = fileparts(fn); nnmn = fullfile(pth,[nmn,'_std',ext...

3 dagar ago | 0

Answered
How to ensure that dsolve provides a trigonometric solution to a second order differential equation?
Since you have a linear ODE with a right-hand-side composed of harmonic terms you know that you can solve for the homogenous and...

3 dagar ago | 0

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Answered
Asymmetric spring with two different stiffnesses
Yeah, I think that should be the correct test. In the modeling you do you have rather big difference in spring constant. When I ...

5 dagar ago | 1

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Answered
Solving differential equation with parameters takes forever
If both x and theta varies with t you cannot solve one first and the other separately later, you should treat them as a system o...

5 dagar ago | 1

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Answered
Code initiates again after exiting while loop which is within an if statement
In your outer for-loop you use you use i as loop-index. The way matlab has implemented things this is done (IIRC) such that ther...

5 dagar ago | 0

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Answered
Asymmetric spring with two different stiffnesses
ODE45 takes a function, f(t,y), describing the differential equation. You have a differential equation something like this w...

7 dagar ago | 0

Answered
I was wondering if this code could be vectorized, and if so, can it be done without conditionals or loops? It would be great if the vectorized form could be written out so that I could run and follow
Sure, you could generate 2 coordinate matrices x and y with meshgrid: nPix = 66; [x,y] = meshgrid(1:nPix); Then you'll have t...

7 dagar ago | 2

Answered
Error: "SVD does not support sparse matrics. Use SVDS to compute a subset of the singular values and vectors of a sparse matrix." while training SOM.
It means that your SOM-training function somewhere uses (or tries to use) the svd function. That function expects a full matrix,...

7 dagar ago | 0

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Answered
Why do colors "gray out" when I save figure as .eps
Ah, from the way your figure looks, it seems the "error-shade" function you use uses alpha-blending - that is colour-patches tha...

10 dagar ago | 0

Answered
1-D Transient Heat Conduction With No Heat Generation [FDM] [Crank-Nicholson]
My suggestion is that you add a line: Tall(:,k) = Tb; at the end of your "time-step"-loop. Then after you're done with it all...

10 dagar ago | 1

Answered
Transposing matrices of a Dataset
Take a look at the help and documentation of the matlab-function permute. HTH

11 dagar ago | 0

Answered
Inversion of block tridiagonal matrices
If you have a small enough problem which is not ill-conditioned just use \, if it is ill-conditioned but you can do an SVD of yo...

11 dagar ago | 0

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Answered
Matlab is installed in ubuntu but i am unable to open it
If you try to execute something like ./matlab from your terminal you tell the shell to run an executable command "matlab" in the...

11 dagar ago | 1

Answered
How to find peaks of the given signal and find the phase shift with respect to the Oscillator 1 signal?
If you had regularly sampled data (it doesn't seem so) this would best be done with spectrogram. That would give you the spectro...

14 dagar ago | 0

Answered
How to solve the reduced eigenvalue poblem
Have a look at the eig function. It solves for eigenvalues-eigenvectors - also for the generalized eigenvalue-problem you seem t...

14 dagar ago | 0

Answered
Plot signal from fits file?
To read data in fits-format you can use fitsread and fitsinfo, but when I try that on an image from SETI-projects web-site I got...

16 dagar ago | 0

Answered
How to make a plot with x-axis that has different scales on different specific regions?
Either you can use something like set(gca,'xscale','log') if that brings you close enough. If you want to plot on some other ...

17 dagar ago | 1

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Answered
Avoid ''Dot indexing is not supported for variables of this type.'', exist(...) isn't working
If you want to check if a struct has a field your're interested in you should check with isfield, check the help and documentati...

17 dagar ago | 0

Answered
editing the JET colormap
You should be able to do something like this: imagesc(peaks(123)) cx = caxis; n_colors = 128 cmp = jet(n_colors); colorbar ...

18 dagar ago | 1

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Answered
How can I check that a newly generated sequence is already in the existing structure list or not?
For example this can be used: intersect([1 2 3;1 3 2;2 1 3;2 3 1;3 1 2],[3 2 1],'rows') % %ans = % % 0x3 empty double matr...

18 dagar ago | 0

Answered
2d interpolation from a non-uniform grid
No you can use griddata and scatteredInterpolant. You can do something like this: Zi = griddata(X(:),Y(:),Z(:),Xi,Yi); And you...

18 dagar ago | 0

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Answered
How could I use MATLAB to solve for x with this equation, 0=a*x^(3)+b*x^(-1)+c.
This works perfectly fine: f = @(x ) -58.8*(550) + 0.5*37*0.002377*x.^3.*(0.02+0.062*((2*960)./(0.002377*37*x.^2)).^2); plo...

19 dagar ago | 0

Answered
Please help me convert them into a function of theta
When you get such an error, your first action would be to look at the sizes of the variables you use: whos r wab L r theta Nex...

19 dagar ago | 0

Answered
ODE 45 range for the variables
If you want to start your ode-integration at an [x,T]-point of [0,298] you have to define your y0 like this: y0=[0 ; 298]; %ini...

20 dagar ago | 0

Answered
Matrix product and inversion speed up
My comment still seems relevant. A simple commandline test gives: tic,AA = ones(3e4,2)*(ones(2,3e4)*ones(3e4,1));toc % Elapsed...

24 dagar ago | 0

Answered
Getting an unknown error on calculating Standard Deviation.
Your variable v is a uint8. Try: std(double(v)) HTH

24 dagar ago | 0

Answered
Evaluate the triple integral and sketch the given solid
Whenever you are faced with a problem to solve start trying to solve it with the methods at hand. 1, You surely know how to do ...

24 dagar ago | 0

Answered
How to make a double integration with numerical integration?
Why not use integral2 to integrate over 2-D domains - it can handle, at least, boundaries in the y-direction that are functions ...

25 dagar ago | 0

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