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Bjorn Gustavsson


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UIT, the Arctic University of Norway

401 total contributions since 2015

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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...

1 day 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...

1 day ago | 2

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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,...

1 day ago | 0

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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...

4 days ago | 0

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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...

4 days ago | 1

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

5 days ago | 0

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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...

5 days ago | 0

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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...

5 days ago | 1

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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...

8 days ago | 0

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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...

8 days ago | 0

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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...

10 days ago | 0

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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 ...

11 days 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...

11 days ago | 0

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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 ...

12 days 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...

12 days ago | 0

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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...

12 days 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...

13 days ago | 0

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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...

13 days ago | 0

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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...

14 days 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...

18 days ago | 0

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

18 days ago | 0

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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 ...

18 days ago | 0

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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 ...

19 days ago | 0

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How to show a deformation of a sphere
Keep track of the x, y, and z-lims or the axis-limits. Something like this: tiledlayout(1,2); [X, Y, Z] = ellipsoid(0,0,0,1,1,...

19 days ago | 0

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Answered
ODE system with variable parameter, Boundary conditions and domain
This could be done something like this: Dall = {0:0.1:1,0:0.1:2}; % however many domains you need etc Y0 = {[Tt01;Pt01;M01],[T...

19 days ago | 0

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Answered
Integrate PDEPE solution wrt x
This rather straightforward method should get the job done (assuming you cannot get away with simply use trapz, or cumtrapz, but...

20 days ago | 0

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How to calculate |x|
abs(x) When you look for functions you should learn about the matlab-command lookfor, have a look at the help and documentation...

21 days ago | 0

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Curve fitting of two different datasets with two different equations and parameters to compare
This is why I never use the fancy curve-fitting-gui-tool, but do it explicitly with fminsearch or lsqnonlin. That way I have mor...

23 days ago | 0

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Answered
How to solve exponential distribution equation using symbolic Matlab?
It helps the int if you explicitly tells what the range to integrate over is: int(f,0,inf) HTH

24 days ago | 0

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Answered
Sturm-Liouville eigenvalues calculation
Have you checked the file-exchange contribution: discrete-orthogonal-polynomial. It solves this kind of problems numerically.

24 days ago | 0

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