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Bjorn Gustavsson


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UIT, the Arctic University of Norway

298 total contributions since 2015

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Answered
Reduce padding around saved image
If you save your edge-enhanced image with something like print -dpng your-image.png you can increase the fraction of your imag...

20 days ago | 0

Answered
Solving an ODE in matlab
First thing you should learn/revise/refresh is how to convert higher-order ODEs to sets of coupled first-order ODEs. You have a...

29 days ago | 1

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Potting Cross-section of an image
First you need to figure out the size of your image - whethre it is an intensity-image or an rgb-image: imsz = size(img); Once...

29 days ago | 0

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Help solving this 2d pde
You are in luck! Matlab provides you with a (rather hidden) method to give you the 2-D Laplacian in matrix form. Have a look at ...

1 month ago | 0

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Dynamic spectra for 1000 files
It is unclear what data you have in your files. Is it frquency and power-spectra from spectrum analyzer? If so then you can simp...

1 month ago | 0

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How to convert video into frames?
Look at the help for VideoReader and especially VideoReader/read, that contains an example of how to extract frames from a video...

1 month ago | 0

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how to input a matrix into a function HELPPP
It sounds as if your new to matlab. If so welcome. Good advice then is to point you to introduction tutorials etc. If you have ...

1 month ago | 0

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problems understanding pspectrum function
The help and documentation to the spectrogram function might be a bit more extensive when it comes to the input parameters you a...

1 month ago | 0

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Plot system of equations
Take it step-by-step. Take pen and paper. Plot a cartesian coordinate system with x1 and x2 at the axes. For 1.6 you have 2 li...

1 month ago | 1

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How can I get the top and bottom envelopes of a signal?
You go to the file exchange and search for envelope. This gave me 157 hits, and should give you the same number of hits, some of...

1 month ago | 0

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difficulty in solving integration of a function
Implement the functions x(t,theta), y(t,theta,H) and F(t,H,p,theta) step-by step. Something like this: y = @(t,theta,H) H+50*si...

1 month ago | 0

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Answered
Hi every one , I need help about:
In order to determine this you need at least one additional piece of information. The camera converts light from incidence angle...

1 month ago | 1

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ode solver , restart from where the simulation ended
Just extract the solution at 1 s from s (i.e. the last row in s). Then simly run the integration from there: t2 = linspace(1,3,...

1 month ago | 0

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Spring mass system subjected to impulse excitation
You seem to have misunderstood how matlab integrates ODEs. Your ODE-function, impulse, should return the derivatives, and , at...

1 month ago | 0

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Is It Necessary to Select an Odd Span for Smoothing Data Using Moving Average Filter?
You can check what happens when smooting by averaging over an even number of points. simply use convolution to carry out the ave...

2 months ago | 0

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dispersion relation normalization ion acoustic
Expand the definitions of and . Then you get a proper expression for the ion-accoustic dispersion relation. To plot it in some ...

2 months ago | 0

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Convert interpolation function to symbolic
You already get a piecewise polynomial out of pchip. That is a symbolic function - though not on the form expected by the symbol...

2 months ago | 1

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How to get a value from inside a function?
So we know something about your functions, but not much more than the most general stuff. If you write your function fun_a somet...

2 months ago | 1

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how to extract variables from ode45
My pedestrian-layman approach to this type of problem is to integrate the ODE, typically with t = t0:dt:tend, then when I have y...

2 months ago | 0

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Infinite recursion in code to graph second order differential equations
Let's analyse what's happening here. When you call odefcn from the command-line 1, the first thing matlab does is to overwrit...

2 months ago | 0

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Scatter 2D plot with specific colorbar
You can try something like this: imagesc % Just to get something to show axP = get(gca,'position'); % Create axes for colorba...

2 months ago | 0

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whats is presice compute time in matlab
These fluctuations are "kind of expected", your computer does a lot of other stuff in addition to running matlab which gives the...

2 months ago | 0

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FFT of sine wave shows unexpected spectral widening
Try this: subplot(1,2,1) plot(templeS) axis tight ax = axis; axis([[-30 0]+ax(2) ax(3:4)]) subplot(1,2,2) axis tight ...

2 months ago | 0

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Answered
Add n days to juliandate
It seems to work just fine as far as I can see. When I compare: jd0 = juliandate(2020, 2, 14); jd0p100 =juliandate(2020, 2, 14...

3 months ago | 0

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How to find the best parameters to fit damped oscillations curves
If you plot your data you should be able to see that the zero-crossings are increasingly further apart. That means that your mo...

3 months ago | 1

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How can I improve code efficiency?
First step of improving code is to run the scripts and functions with the profiler on (seel documentation and help for profile) ...

3 months ago | 0

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Some question about a special code for solving an ODE system by Runge-Kutta method
Since u1 and u2 depends on p1, p2 and p3, that in turn will depend on time, you have 6 coupled ODEs. The best(?) way to solve th...

3 months ago | 0

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Curve fitting of a custom equation with a predefined value
For this type of problems I typically use the basic optimization-functions of matlab - either fminsearch or lsqnonlin depending ...

3 months ago | 0

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how to get eigenvalues of a function matrix?
To calculate the eigenvalues of H you have to chose, either to use your implementation where H is a handle to a function returni...

4 months ago | 0

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How do I create a new folder each time I run a code?
This is easily solved: dirname = fullfile(path_2_root_dir,sprintf('NewFolder-%s',datestr(now,'yyyymmdd-HHMMSS'))); mkdir(dirna...

4 months ago | 0

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