Star Strider

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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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Answered
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

Answered
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

Answered
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

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please help me (dsolve)
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

Answered
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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Answered
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

Answered
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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Answered
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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Answered
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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Answered
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

Answered
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

Answered
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

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Chi-squared for multiple groups
Consider Perform One-Way ANOVA instead.

2 days ago | 0

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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

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designing a chebyshev type 2 high pass filter
Start with the cheb2ord function to define all the variables appropriately.

3 days ago | 0

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Answered
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

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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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Answered
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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Answered
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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Answered
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

Answered
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

Answered
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

Answered
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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Answered
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

Answered
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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Answered
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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Answered
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

Answered
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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Answered
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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Answered
Predicting the kinetic constant of a reaction based on experimental data
If you have the Global Optimization Toolbox, the code I attached will estimate the parameters with reasonable accuracy, although...

7 days ago | 0

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