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# Star Strider

##### Last seen: Today
15,104 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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Can't plot a graph no matter what I do
Eliminate the elseif call and it works! (The elseif is not necessary anyway.)

39 minutes ago | 0

MATLAB stem function error
Either just use ‘z1’, or use a ‘shape’ argument with conv: n = -15:15; u = n>=0; u1 = n>= 4; f = u-u1; z1 = conv(f,f,'same...

1 hour ago | 0

Draw shapes not in a graph
Try something like this: x1 = rand(1,5); y1 = rand(1,5); x2 = rand(1,7); y2 = rand(1,7); figure plot(x1, y1, 'or', 'Mar...

3 hours ago | 0

The single quotation marks are likely the problem. Try this slightly edited version: syms y(t) Dy = diff(y); D2y = diff(...

3 hours ago | 0

How Do I Fitting a 3 Unknown Parameter Model?
There are several functions available to estimate the parameters. This uses fminsearch because everyone has it: VFTfcn = @(b,...

1 day ago | 0

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Matlab interpolation between two surfaces
Experiment with this: x = linspace(-5, 5, 20); y = x; [X,Y] = ndgrid(x,y); z = @(x,y,s,h,a) a .* exp(s*(x.^2+y.^2)) + h; ...

1 day ago | 0

complementary error function (surf plot)
Add: [X,T] = ndgrid(x,t); and it works: x = linspace(0,10^(-6),20); t = linspace(0,5,5); [X,T] = ndgrid(x,t); u0 = 10^(-...

1 day ago | 0

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Solving equations using Laplace transform
Unless you are solving a partial differential equation, such that the Laplace transform produces an ordinary differential equati...

2 days ago | 0

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Answers editor seems to be broken
The website was updated. I had the same problem, and it turned out that Rena’s suggestion that clearing the Firefox cache solve...

2 days ago | 0

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Error using atan2 Inputs must be real.
If you want to compute the phase angle of a complex number, use the angle function.

2 days ago | 0

How to get unknown number of variables to be all same length through interpolation
Try this approach: V1 = sort(rand(1,5)); % Original Vector V2 = sort(rand(1,10)...

2 days ago | 0

ode15s error（Genetic algorithm for differential equation parameter identification）
I cannot follow your code. See Ode system solution with unknown constant for one example of an approach that generally works....

2 days ago | 0

Chi-squared for multiple groups

2 days ago | 0

ODE with time-varying coefficients
The Answers Comment and Answer windows are malfunctioning. I am having serious problems with the lack of formatting and other o...

3 days ago | 0

designing a chebyshev type 2 high pass filter

3 days ago | 0

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Differential eq of a hot storage tank
The time intervals the ODE solvers use are whatever you define them to be, since they have no inherent unit. In the ‘m’ assignm...

3 days ago | 0

Output numeric array from symbolic evaluation
After the loops: T = vpa(T) creates the entire array as decimal fractions.

3 days ago | 0

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How can I draw the fitted curve and find the initial slope of the attached plot?
Try this: D = readmatrix('Example.xlsx'); x = D(:,1); y = D(:,2); p = polyfit(x, y, 3); yfit = polyval(p, x); dp = poly...

4 days ago | 0

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Mathematical Modelling for parametric analysis
See the documentation for regress to understand how to work with the ‘carsmall.mat’ file. You should have it, since it’s been...

4 days ago | 0

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Invalid indexing for dsolve
The equations are nonlinear, and for most nonlinear differential equations, an analytic solution does not exist. Try this ins...

4 days ago | 0

How to extract numbers from .dat file
One option: fidi = fopen('Nasis Vangelis.dat','rt'); k = 1; while ~feof(fidi) readline = fgetl(fidi); C{k} = regex...

4 days ago | 0

How to Plot a Continues Tiime Signal
I have no idea what ‘x(t)’ is. I usually code the uint step function as: u = @(t) t>=1; althoug other options are possible...

5 days ago | 0

read data from delimited text file
This is one of the more difficult files I have managed to import! See if this does what you want: fidi = fopen('water.txt')...

5 days ago | 0

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A simple LowPass Filter
Using a window inplies a FIR filter. Start with the fir1 function to design it, and freqz to analyse it. Filter your signal wi...

5 days ago | 0

Printing my Integration step by step
Use cumtrapz instead of trapz: L=F./W; lambda= 2*cumtrapz(W,L) figure plot(W, lambda) grid xlabel('W') ylabel('\int\la...

6 days ago | 0

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Cell-Matrix, I can't extract values
Change the code slightly to: F = openfig('phi_1.fig'); ax = gca; lines = findobj(ax, 'Type','Line'); for k = 1:numel(lines)...

6 days ago | 0

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Mesh with griddata, how eliminate undesidered extra surface
Without your data, posting an exact solution (if one even exists) is not possible. One possibility is that your data are actu...

6 days ago | 1

why surface plot is connecting its edges?
Try this for the file provided, and the others that likely have similar formats. Note — It is only necessary to reshape the ...

6 days ago | 0

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Help finding R^2 value for curves
I appreciate your quoting my code! The value is not difficult to calculate. One example using a much simpler single-var...

7 days ago | 0

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