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John D'Errico


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4,680 total contributions since 2006

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Answered
Solving 2nd part of minimax question
I see you did answer the question in my comment. "mmr, a row vector containing the absolute values of the difference between th...

5 hours ago | 1

Answered
How does ode23 works?
Literally impossible to answer. A copmplete answer would involve teaching a class on numerical methods for ordinary differential...

3 days ago | 1

| accepted

Answered
SVD and basis of a plane
Lets make some random data. X = rand(1000,2)*rand(2,3) + rand(1,3); I have no idea what plane represents the data, but I do kn...

4 days ago | 0

| accepted

Answered
How to separate a variable out of trigonomic expression
As has been pointed out, this is not remotely a question about MATLAB, but you have gotten two answers already, so let me point ...

4 days ago | 1

Answered
return the numerator and denimentor
Rat gives rational results for a floating point number, sometimes they are only approximate, of course. [n,d] = rat(1/2) n = ...

6 days ago | 0

| accepted

Answered
2D Convex Hull: I can't think of a 'criteria' to filter out the 'wrong' points, please help!
It does not seem you have done anything at all. Write some code. Get started. Play with it. Find a way to overcome the problems....

12 days ago | 0

Answered
Nelder and Mead Algorithm
I'm trying to be retired from Answers, but having glanced in, I see this question, one which I am pretty well qualified to answe...

16 days ago | 2

Answered
Distinct sum of 3 variable which ranges between 1-255
As you recognize yourself, if you simply form the sum of three integers, you cannot then recover the original values from only t...

1 month ago | 2

| accepted

Answered
How to initialize an array such that the values satisfies an equation
Too bad, in the sense that for smaller L, say on the order of 8 or so, this is not that difficult to do exactly. (I have written...

1 month ago | 1

Answered
Solving non linear equations sytem
I would reduce this to a 2 variable problem first. That is, use equation 1 to solve for x1. x1 = b1/cos(a1 + x2) Likewise,...

1 month ago | 1

Answered
sparse to gridded 3-D interpolation
First, should MATLAB use all of the CPU capability? That is difficult in what you are doing, becaue it is not easily parallelize...

1 month ago | 0

Answered
Regularization for Non-linear fitting with fitnlm.
(Please don't add answers to make a comment. Use comments for that.) But how can you do a simple regularization on the coeffici...

1 month ago | 2

Answered
185k1*185k Matrix
Think of it like this: If all of the elements in that matrix are non-zeros, then you have 185000^2 ans = 3.4225e+10 So 3...

1 month ago | 0

Answered
A function to find prime number
Hey, you wrote some code! Credit for that. :-) But what did you do? function isPrime(number) tf=isprime(number); if tf==tru...

1 month ago | 0

Answered
Question about the tolerance of lsqcurvefit
This is not a problem of lsqcurvefit tolerance. Instead, see that the error makes a statement about INTEGRATION tolerances. That...

1 month ago | 0

| accepted

Answered
I am trying to integrate IMU and GPS data to find roll of ground vehicle on the same road at different velocities. But, I am getting inconsistent results and an error at higher velocities (45mph) compared to lower velocities(25mph).
The singular matrix suggests why it is you are getting garbage, as once you have that, nothing will likely make any sense. Is th...

1 month ago | 0

Answered
Linspace with varying increment
The problem is, vendor provided software cannot work like that. You have descibed several cases of potential interest to you, fr...

1 month ago | 1

Answered
Linear Constraint based on two variables fmincon
Why, if you already have other inequality constraints, is this a question? And how you wrote it, using A is inconsistent with yo...

1 month ago | 1

Answered
I need to solve an equation involving squares and cubes.
You have many values for both d and p? Do you want to solve it for all combinations of d and p? Anyway, first, I would recogniz...

1 month ago | 1

Answered
decrease calculation accuracy to speed up running time
You essentially cannot do what you want, with one small caveat. That is, you canot arbitrarily tell MATLAB to do all computation...

1 month ago | 3

Answered
how to plot an ellipse having her equation?
First, learn how to write a function. fun = @(x,y) x.^2 / 25 + y.^2 / 9 - 1; Note the use of the .^ operators. They will be im...

1 month ago | 0

Answered
Unable to predict data well enough
I would point out that your code shows you using the first SEVEN data points, not the first 10, despite your claim otherwise. n...

1 month ago | 0

Answered
how can i find the intersection point between the vertical lines and the curve (xmin,ymin) ?
The red curve is a piecewise linear interpolation, not really a curve, just connect the dots by the plotting routine. The green...

1 month ago | 1

| accepted

Answered
lsqcurvefit: is the output of this function unique for a given set of initial conditions (and deterministic model)?
The problem is, that is not your code. Not all of it. That is just how you call lsqcurvefit. We do not see the pandemic1Dall2 co...

1 month ago | 1

Answered
change a logical array value based on the index of another matrix
If you want to create x on the fly, then just do this: x = A > 4; If you for some reason really want to modify an existing vec...

1 month ago | 0

| accepted

Answered
What's the meaning of instrucment sound in Matlab?
Let me just answer this as if you asked for an explanation of what a sound is in the world of MATLAB. For example, if we try: l...

1 month ago | 0

Answered
vector to upper and lower triangular matrix
What you fail to see is that while your code works for a 3x3 matrrix, it must always fail for any n other than n==3. You want t...

1 month ago | 0

| accepted

Answered
double differentiation and double integration of sine wave
This is not a question about MATLAB, just understanding some basic mathematics. At least, understanding calc 101. First, you ne...

1 month ago | 0

Answered
Diagonal/Symmetric matrix
I don't even think your code works for a 3x3 matrix. The matrix it produces is OD OD = 81 23 18....

1 month ago | 0

| accepted

Answered
How do I open a pcode (.p) file created in a version older than MATLAB R2007b? My Matlab version is R2018b.
You cannot edit a .p file, if that is what you mean by open. That is true in any version. If the .p file is too old, but you s...

1 month ago | 0

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