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# Bjorn Gustavsson

### UIT, the Arctic University of Norway

282 total contributions since 2015

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Answered
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...

10 dagar ago | 1

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Answered
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...

14 dagar ago | 1

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Answered
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...

15 dagar 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...

16 dagar 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...

20 dagar 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...

21 dagar 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 ...

22 dagar 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...

28 dagar 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...

29 dagar 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) ...

ungefär en månad 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...

ungefär en månad ago | 0

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Answered
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 ...

ungefär en månad ago | 0

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Answered
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...

2 månader ago | 0

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Answered
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...

2 månader ago | 0

Answered
Images don't show properly with imshow after certain calculation
When you do things like this the errors are always (in my experience) in different normalizations and type-castings. To work the...

2 månader ago | 0

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Answered
Press " " to rename 4 instances of "VariableName1" to "VariableName2"
That ought to be the return key... HTH

2 månader ago | 0

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How to compute SVD of a matrix without using in-build SVD command?
So this is a homework task, right? (Unless you come up with a good reason this is the case everyone have to come to this conclus...

3 månader ago | 0

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analytical solution of ODEs
This should be done thisly: syms r syms T(r) dTdr = diff(T) d2Tdr2 = diff(T,2) T = dsolve(1*d2T+((1/r)*dT) ==1,T(0.005)==20...

3 månader ago | 0

Answered
How to graphically/interactively select region of interest from 3D point cloud data
In newer versions of matlab there seems to be just such a feature, see: ROI.CUBOID For older versions of matlab (I vaguely rec...

3 månader ago | 0

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Answered
Obtaining a equation in two variables (x and y) from a set of data points
What you should do depends on your objective. If you very explicitly want a function you could use spap2 (and perhaps some of it...

3 månader ago | 1

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Answered
Hello, we have received a Matlab code in school and the assignment is to explain what it means. I wonder if anybody could take us through the code and explain it?
At the matlab command-line prompt type: dpstop in nameiofscript where nameiofscript is the name of the script-file. Then you r...

4 månader ago | 0

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How to obtain CDF from large dataset?
Have a look at the help and documentation of the function ksdensity - that is one way to do this with the least amount of assump...

4 månader ago | 0

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Difference in frequency domain between mp3 and wav
There are some small differences. You should also try to compare the spectrograms of the two signals, see the help for spectrogr...

4 månader ago | 0

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How to edit matlab saved file?
I think something like this should work: filename2edit = 'something.mat'; load(filename2edit,'X2change') X2change(3) = 12; s...

4 månader ago | 0

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I would like to plot Histogram and relative frequencies from a given dada.txt. I already plot time series plot for the given data. KIndly help me to plot histogram and relative freqs.
Have a good look at the help and documentation of histogram function. It should let you solve this task easily. HTH

4 månader ago | 0

Answered
Solving 4th order ode problem
In general you convert a high-order ODE to a set of first order ODEs like in this example below (I will use a simple equation of...

4 månader ago | 0

Answered
partial differentating a matrix by a vector
Have a look at the help and documentation for jacobian. HTH

4 månader ago | 0

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Answered
Is it possible to plot a 3D graph with non numerical values?
The simplest method might be to map your classes to some integer range and then use the standard plotting functions. In your cas...

4 månader ago | 0

Answered
How to display figure in full-screen mode programmatically and save as a high resolution image?
To save as high-resolution, I regularly use: print('-depsc2','-painters','J.eps') If you desperately want the image as a png-i...

4 månader ago | 1

Answered
How to store 2D variables in matrix
For the storing the point coordinates you might look at either cell-arrays: r1 = [1,2,3]; r2 = [3,2,5]; r3 = [4.5,pi,1,5]; %...

4 månader ago | 0

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