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John D'Errico


Retired

Last seen: Today Actif depuis 2006

DON'T contact me, as too many students then decide I am their personal consultant if I allow it. Anyway. I won't answer questions. PERIOD. I don't do your homework. I won't do consulting by mail. A retired mathematician, numerical analyst, woodworker, bridge player.

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A répondu
How to find the angle between two hyper planes?
Will you please learn to use arrays? You have moved from 2-3 to now 6 dimensions in your questions. When you are one day trying ...

environ 13 heures il y a | 0

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Is there any Matlab finction to compute an integration using Rmberg method?
Not exactly. For example, if you look up Romberg integration, you will find it is based on Richardson extrapolation, but at leas...

environ 14 heures il y a | 1

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Excel Solver least squares vs MatLab optimization
fminsearch is never a tool you want to use if you want any kind of strong convergence. Sorry. But comparing anything to fminsear...

1 jour il y a | 0

A répondu
Problems with the parallel inversion of a large, sparse and linear system in Matlab
You should NEVER be inverting a large sparse linear system. The result will generally not be sparse, so you will then gain nothi...

1 jour il y a | 0

A répondu
curve fitting using least square method form equation , y = (1 + a sin(2x))/ (b + cx^2) where a, b, c are unknown real constants.
Hint (since this is homework): What is your model? WRITE IT DOWN. What happens when you mutiply by the term in the denominator? ...

1 jour il y a | 0

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A répondu
TriscatteredInterp on a multi-core computer
A long dead question. But even today, you won't easily find tools like triscatteredinterp, or griddeInterpolant, that will work ...

1 jour il y a | 0

A répondu
Solving a 2nd order ODE for specific parameters
Did you try it? What did you try? For example, I started with what you said. YOU CANNOT use ODE45 to solve a problem where the p...

1 jour il y a | 0

A répondu
difference between Matlab v7.9 and v6.5
which abstractAngleConv -all That is part of the mapping toolbox, but not something that is accessible directly to a user. So y...

1 jour il y a | 0

A répondu
adjusting the peak of a spline in curve fitting
Um, you are not being very clear here, probably because you don't totally appreciate what you are asking. Certainly you have not...

1 jour il y a | 0

A répondu
I think I need a for loop, but I don't know how to do it.
[x,y] = meshgrid(1:3,[2 3 5]) z = x+y If you need it as a 9x1 array, then just unroll the arrays into vectors. z = z(:) Star...

2 jours il y a | 0

A répondu
Maximum of 2D data interpolation
You will NEED to use a spline based method of interpolation here, specifically spline or cubic. NOT makima, or pchip. Those inte...

2 jours il y a | 0

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How to use if/then to assign a year to a set of dates?
Easy peasy. :) data = [8 7 2000 12 9 8 2000 14 9 9 2000 13 3 11 2001 11 8 3 2001 17 12 15 2001 14 2 2 2002 10 5 1 2002 9...

2 jours il y a | 2

A répondu
invalid use of operator
Looks great. Except, what you have written is not valid MATLAB syntax. Why do you think you needed to include the :end in there...

2 jours il y a | 0

A répondu
I need help to determine the distribution type for my set of data
You CANNOT know what distribution any set of nummbers were generated from. That is provably imposssible. For example: x = 0.432...

2 jours il y a | 0

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Unable to solve nonlinear equation using fsolve as the message shows No solution found
I would not be at all surprised if it was poor starting values that might cause the problem. syms x y F1 = -9.135789053E+00-lo...

3 jours il y a | 1

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Deconvolution results a single value
Convolution of two vectors yields a new vector that is longer than either of them. So if the vectors have length N and M, then t...

3 jours il y a | 0

| A accepté

A répondu
Files added to path won't run unless I rename them first.
Never use the directory structure that comes with MATLAB to store your own files. Why not? MATLAB caches those directories at s...

3 jours il y a | 1

| A accepté

A répondu
manipulation of yearly, quarterly, monthly, weekly and daily dates using datenum
I don't see the problem. It mainly looks like you need to understand the concept of leap years. That would be crucially importan...

4 jours il y a | 0

A répondu
Cubic Spline not printing
It has been a month since you asked the question, so I'll post an answer. Note that your data has x=[1 2 6 3 5 6 7 8 9 7 6 5 ...

4 jours il y a | 0

A répondu
Does the built in function singular value decomposition (svd) do the correlation matrix for you?
The SVD does NOT perform the re-scaling involved in a correlation matrix. It just uses the array you give it, with no preemptive...

4 jours il y a | 0

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A répondu
finding fold curve in 3D surface
You have a surface, generated using meshgrid. I would split that surface into a triangulated mesh. So two triangles per rect in ...

5 jours il y a | 0

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A répondu
Difference fit result form nlinfit and lsqcurvefit
And, so? Many problems will have multiple locally optimal solutions. Neither of those tools even hopes to be a globally optimal...

5 jours il y a | 0

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Define a family of functions
DON'T DO IT THAT WAY. Instead, define ONE function. One function to rule them all. (Sorry. That last part just slipped out.) Se...

5 jours il y a | 1

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A répondu
Draw the sphere to find the radius of the sphere
Estimation of the sphere parameters is not too difficult. First, since you have shown no data, I'll make some up. XYZ = randn(5...

5 jours il y a | 0

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A répondu
How can I generate a trigonometric formula for the following case?
Theta= [39.8414239035357 38.0423831220740 35.9925962696569 33.6629179282453 31.0086860615562 27.9576609766453 24.3833553424339...

5 jours il y a | 2

A répondu
Randomize vector avoiding consecutive values
Typically, rejection would be necessary. Of course, if your initial vector were composed only of two elements, then there are on...

6 jours il y a | 0

A répondu
What does this plot mean? Can an equation be made of it?
Can you get an "equation" for it? No. At least not any more than what you already have. Anyway, an equation involves an equality...

7 jours il y a | 0

A répondu
is that really necessary to measure and put the weakness of the thesis if it is not scope of the work?
This is totally inappropriate to Answers, since it has nothing to do with MATLAB. Even if MATLAB would be involved with your the...

7 jours il y a | 0

A répondu
Data fitting using thin-plate spline/interpolation
This is a common problem people have with splines in any form. They hope to see some nice simple function they can write down. M...

8 jours il y a | 2

A répondu
How to display a message as flashing and in my desired color and font size?
You can do that, but since disp is not written to accept those extra arguments, it might not work. Wanting code to do what you w...

8 jours il y a | 1

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