Community Profile # Bjorn Gustavsson

### UIT, the Arctic University of Norway

Last seen: Today Active since 2001

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3 Differential equation using 4th order runge kutta
You have a function for a 2-D system of ODEs. That then is messed up: function diffeqs =ode_Q10(t,var) % t = var(1); % This ov...

ongeveer 6 uur ago | 0

Rotation Matrices - omega phi kappa vs yaw pitch roll
If you have mixed up the order of the rotations you might step through the different combinations of rotations and sign-conventi...

1 dag ago | 0

How can I perform large sparse matrix multiplication efficiently when one sparse matrix is block diagonal?
Shouldn't straight summation be preferable for the calculations of sums rather than doing it by way of matrix multiplication. Pe...

1 dag ago | 0

How can I convert deformation data into FRF using FFT?
Simply use fft? That will give you the complex discrete Fourier-transform. If you do: fS = fft(S); % fS will have "DC"-componen...

1 dag ago | 0

How to differentiate between an index and a value in a function?
Your function J expects a single input as defined. I get: J_0 = J(x_0); to run without problems... HTH

1 dag ago | 0

Looping through 4 Images that have fixed names
You can for example put the filenames into a cell-array: imFileNames = {'im1.jpg','im2.png','im3.jpeg','im5.tiff'}; Then you c...

2 dagen ago | 0

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Why am i getting this error message? "Array indices must be positive integers or logical values."
In matlab (and most other programming-languages) you will have to write out the multiplication-operator (* for matrix multiplica...

2 dagen ago | 1

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Does anyone have the periodic cubic spline codes in matlab?
You will find plenty of examples of spline-tools with different levels of support for periodic boundary-conditions on the file e...

2 dagen ago | 0

Multiply two griddedInterpolant functions
If you have 2 functions f(x,y) and g(x,y) you can evaluate the product on your selected grid-points and multiply them: fx_at_xy...

3 dagen ago | 0

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History function for ODE45
Since ode45 solves systems of first-order differential equations on the standard form the history does not matter, so I've never...

3 dagen ago | 1

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how to plot two different plots with different axis in a single graph?
Have a look at the documentation and help for yyaxis. There you should find illustrating examples doing what you want. Possibly ...

3 dagen ago | 0

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How to write a code for plotting a Poincare map for the analysis of a double pendulum and also How to simulate the motion of the double pendulum.
You will find a couple of contributions on the file exchange for Poincare-maps, the first seems promising: FEX-hits on "poincare...

6 dagen ago | 0

area of water body in a grey color image
If the water-surface are flatter than the not-water-surfaces (seems reasonable assumption for standard optical satellite imaging...

7 dagen ago | 0

solve a complex second order differential equation
The first step is to convert your second-order ODE to two coupled first-order ODEs: Then you should write that ODE-system as ...

8 dagen ago | 0

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2D Minimization problem, not good for fminsearch?
For problems like these (It seems likely that your function has multiple local minima or at least very very flat regions) the be...

9 dagen ago | 0

Error using * Incorrect dimensions
For problems like these you should learn to run the code line-by-line at the command-line prompt. Then check the size and type o...

9 dagen ago | 0

Can someone please drop the code for ICA( independent component analysis) for image segmentation on matlab for classifying thermal images
Look on the file exchange for ICA-implementations: ICA at FEX Get fastICA from the/(a significant) source: FastICA Then the ma...

9 dagen ago | 0

Integer eigenvalues in Matlab
Since you have a matrix and want the eigenvalues then the best approach seems to be to actually calculate the eigenvalues. For t...

13 dagen ago | 0

How to solve simultaneous equations?
Using symbolic tools you have solve - look at the help and documentation for that function for examlpes. Your problem should red...

14 dagen ago | 0

How to extract data from a function or functions. Also how to export this data to excel.
Your functions have their own name-space where the variables that are defined exists (in addition to the input variables that yo...

14 dagen ago | 1

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how to Solve 4 Equation and 3 unknown
When you have four non-linear equations with three unknowns you cannot, in general, expect to get a symbolic solution. For these...

15 dagen ago | 0

fitting data to system of ode
You will find the answer to this problem in a link to yet another answer (by Star Strider) here: fit-a-parameterised-ode-solutio...

15 dagen ago | 0

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How to solve differential equations with varying constants
For the case you describe you have to add information about how X and p varies with time. Are they constant over some fixed inte...

16 dagen ago | 0

What should go in a next-generation MATLAB X?
Allow elementary mathematical operations on function-handles. So instead of writing the sum of two functions as: f1 = @(x) x.^2...

16 dagen ago | 0

Plotting spectrograms for multiple files
Wouldn't you achieve the desired output by putting the different spectrograms in consecutive subplots? Something like this perh...

22 dagen ago | 0

How to define constraint in Optimization such that difference in value between two consecutive unknowns is not greater than 50%
Perhaps a constraint-function like this would get the job done (might be used with fmincon for example): function [c,ceq] = you...

22 dagen ago | 0

Using fsolve to solve equation system for coefficients of a Schwartz-Christoffel map
You can use the optimization-functions to get a solution, or a hopefully good starting-point for fsolve. If you define a sum-of-...

22 dagen ago | 1

Plot handle not being assigned
When you plot multiple lines plot returns an array of line-handles then it doesn't work to assign those to one element in h. For...

23 dagen ago | 0