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# Star Strider

##### Last seen: Today
13.464 total contributions since 2012

Hic sunt dracones!

PROFESSIONAL: Physician (M.D.): Diplomate of the American Board of Internal Medicine; M.Sc. Biomedical Engineering: Instrumentation, Signal Processing, Control, System Identification, Parameter Estimation

NON-PROFESSIONAL: Amateur Extra Class Amateur Radio Operator; Private Pilot, Airplane Single Engine Land, Instrument Rating Airplane; Gamer

NOTE: I do not respond to emails or personal messages, unless they are about my File Exchange contributions.

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Area under FFT curve
Calculate the areas of only the ‘positive frequencies’ half of the fft output, not the entire output. If the data are all posit...

37 minuti ago | 0

Need to solve the roots from a large equation
Use the correct values for ‘la’ and ‘n’, then this: syms k la = 42; n = pi; Eqn = 2*k - 2*k*n + (8*k^7*n^4 - 24*k^5*n^3 + ...

circa 11 ore ago | 0

Find Middle of square wave
Use the islocalmax function (R2017b and later): This code plots green upward-pointing triangles at the centre of each pulse: ...

circa 20 ore ago | 0

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Change color of a specific line in mesh
No exact solutions without your code and data. One approach: xv = -15:0.8:15; yv = -10:0.8:10; [X,Y] = ndgrid(xv, yv); z...

circa 23 ore ago | 1

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Calculating efficiency using matlab
No loops needed: Tout = [323.2 326.0 328.8 331.6 334.3 337.1]; I = [500 550 600 650 700 750]; [Toutm,Im] = ndgrid(Tout,I...

circa 24 ore ago | 0

Vary a parameter and plot the output
Try this: function main x0 = [500 500 500 500 5 5]; opt = optimset('Display','off'); % 'display', 'iter' I = [500 550 600 ...

2 giorni ago | 0

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How do I avoid using a lot of if statements in a row?
Another option is switch,case,otherwise. You will need to determine if that is an improvement over the multiple if blocks.

2 giorni ago | 0

Stability Analysis (Dertermining the Limit Cycle)
The phase portrait is usually plotted as the function against its derivative. Use the gradient function to calculate the deriva...

2 giorni ago | 0

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Peak to Peak Value of Sinusoidal Grad
Use the islocalmax function to find the maxima, islocalmin to find the minima, and go from there. (These functions were introdu...

3 giorni ago | 0

Solve numerically a system of first-order differential equations
Create the function symbolically: syms a b c d e f g t x(t) y(t) z(t) T Y Dx = diff(x); Dy = diff(y); Dz = diff(z); Eqn1 ...

3 giorni ago | 1

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Finding Angular Frequency of an Oscillation
Likely the easiest way would be to find the times of the positive peaks, then calculate from there: [pks,pktimes] = findpeaks(...

3 giorni ago | 1

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filter a timetable by day
I am not certain what you intend by ‘groups’. One option is to use the retime function: TTRT = retime(TT, 'daily','mean') ...

3 giorni ago | 0

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how do i keep the format of xticklabels?
Use compose or sprintfc to create the cell array of labels: figure plot(0:6, rand(1,7)) xtl = sprintfc('%d',10.^(0:6)); xtl...

4 giorni ago | 0

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creating plane piecewise in one plot
Try this: f = @(x) (3*x).*((0<x) & (x<=1)) + (2*x+1).*((1<x) & (x<=2)) + (6*x+1).*((2<x) & (x<=3)); x = linspace(0, 3); ...

4 giorni ago | 0

Try this (obviously with your data, not my simulated vectors): x = 1:50; ...

4 giorni ago | 1

"dsolve" gives some extra terms in the solution
Tell simplify to keep simplifying until it either meets the iteration limit or cannot simplify the expression further: Vs= sim...

4 giorni ago | 0

Nans values in time series
You must decide that. There are methods to interpolate the NaN values if you want to do that, one of which is the fillmissing...

5 giorni ago | 0

How can I solve an equation containing log ?
Use the fsolve function, because it will return complex results, and since the argument to the log function is negative it will ...

5 giorni ago | 0

How to find maximum of a function of 2 variables
One approach: z = @(x,y) cos(x.^2 + y.^2); XY = fminsearch(@(b)norm(-z(b(1),b(2))), [3; 3]) producing: XY = 2...

5 giorni ago | 1

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convert a transfer function to controllable and observable canonical form
num = [4]; den = [1 0.8 4]; Gp = tf (num , den); The canon function requesting the 'companion' canonical form directly produc...

5 giorni ago | 1

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why do I get "Undefined function or variable 'tspan'."
The code defines that variable as ‘timespan’. The argument names and the varialble names must always match. Try this: [t,z...

6 giorni ago | 1

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How to graph values of a function above and below 0 as separate functions?
Subscript the elements and provide corresponding time vectors for each one: t= 0:0.2:3*pi; y=sin(t); for k = 1:numel(t) ...

6 giorni ago | 1

plot function y axis
Put: ylim([1 100]) after the plot call.

6 giorni ago | 0

plot function y axis
Put: ylim([1 100]) after the plot call.

6 giorni ago | 0

How can I combine several file.fig together
For each .fig file: F = openfig(filename); Lines = findobj(F, 'Type','Line'); Then, for each element of the ‘Lines’ array: ...

6 giorni ago | 0

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Use entries of symbolic array outside of the array
The reason is that the elements of ‘X’ are stored as matrix elements. The individual elements exist only as matrix elements, no...

6 giorni ago | 0

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What should the order of my FIR filter be?
The fir2 function documentation appears to favour even-numbered filter orders. (The only MATLAB functions that I know of that c...

7 giorni ago | 0

Finding and Graphing FWHM (Trouble with Find Function)
Without ‘data_10micronslit.txt’, it is impossible to provide a specific solution. However the findpeaks function will return th...

7 giorni ago | 0