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John D'Errico


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Retired

5.125 total contributions since 2006

(Don't contact me. I won't answer questions.) A retired mathematician, numerical animalist, woodworker, bridge player.

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Answered
numerical solution of a system of ODE which is not in standard form
Your question seems to be one of solving a system of ODEs with a mass matrix. For example in the help for ODE45, we see this opt...

1 dag ago | 1

Answered
calculate tension by raphson newton in matlab
You have indicated these coefficients, although I worry there may be issues, because of the use of lower versus upper case W, et...

1 dag ago | 0

Answered
Interpolating n-dimensional functions
First, IF you have a complete gridded lattice, then you don't want to use griddatan. That is DEFINITELY a BAD idea. Why? Because...

1 dag ago | 0

Answered
What am I missing here?
Thank you. That makes it much easier for someone to offer you help. Now I'll be willing to look at the problem you had. It loo...

2 dagen ago | 1

Answered
How to extrapolate a contour plot?
Let me see. You have data in only 25% of the region of interest. Now you want to extrapolate that data into a region that compri...

3 dagen ago | 0

Answered
To solve non-linear equation by inversion notion
STOP. Is this nonlinear? Or is it linear? A*X = b is still LINEAR, even if the array is not square. Even in the linear case, t...

3 dagen ago | 0

Answered
how to use reshape ?
The good thing about reshape is IF you put in an empty argument, then it figures out how many columns you will need. But first,...

3 dagen ago | 2

Answered
Is an infinite for loop infinite?
We can always try it. Perhaps we can learn something about how the loop works, done by a careful test. Remember that doubles are...

3 dagen ago | 1

| accepted

Answered
how to fit 3 lines with one equation
Easy to answer. Is it possible? Of course. Anything is possible, though it may take a heck of a lot of work. I could even fin...

5 dagen ago | 0

Answered
Image Processing on point clouds
If you want to use image processing tools, you pretty much need an image. Those tools are not written to work without one, certa...

5 dagen ago | 0

Answered
Error in Eigen Values
Is KSr a double precision matrix, or a function, in the form of a function handle, or the name of an m-file function? That seems...

5 dagen ago | 0

Answered
Multiplication of two polynomials having different variables
The simple answer is to use the symbolic toolbox. If you have it, I cannnot think of a good reason why you would not use it. sy...

5 dagen ago | 0

| accepted

Answered
geometric progression and multiply by a common variable, help me pls.
So, you want this? B = 3; C = B*20*sqrt(2).^(0:10) C = Columns 1 through 9 60 84.853 120 ...

7 dagen ago | 1

Answered
f(x,y)<=0
I can see several ways off the top of my head. Consider some arbitrary implicit function. fun = @(x,y) x.^2 + y.^3 - 3; Easy ...

7 dagen ago | 0

Answered
how to decode the message 67 44 41 49 39 19 113 76 62 104 69 55.
A good clue to the answer "Is this code correct", when applied to a homework assignment like this is if you get something that m...

7 dagen ago | 0

Answered
Baseball trajectory with drag and wind
This is almost a classical problem, and the reason stiff ODE solvers were provided. Essentially, when you get that error using O...

7 dagen ago | 0

Answered
Generating dispersed (non-integer) random matrix/array that sums to a particular value
I think you do not understand what you are asking. randfixedssum indeed produces results that are uniformly sistributed within...

8 dagen ago | 0

| accepted

Answered
What frustrates you about MATLAB? #2
That the mind reading toolbox has never become available for general use? ;-) Truly, that scares me just a bit if it ever truly...

8 dagen ago | 2

Answered
Code to produce orthogonal rows in a N* N matrices
Not that hard. First check, is this homework? Hmm. Highly unlikely, since I had to think for at least a second about how to solv...

8 dagen ago | 2

| accepted

Answered
Double integration of a binomial function (in x and y) generated from two row arrays
I follow what you did (possibly) A = 10; B = 20; a = [0, 1, 2, 3, 4]; b = [5, 6, 7, 8, 9]; syms x y x = sym('x'); y = sym...

9 dagen ago | 1

| accepted

Answered
Bilinear and Trilinear Interpolation
Wow. I guess I've been working with those tools for so many years, as well as building variations of them, that I think of them ...

9 dagen ago | 1

| accepted

Answered
How to solve PDE problem
This is second order in the time derivative, so there is a utt term. But that should make in not in the realm of pdepe, which al...

9 dagen ago | 0

Answered
1D Linear Elasticity Equivalent Stiffness Solution not being solved (6 equations and 6 vars)
These are differential equations, a boundary value problem. We use dsolve to solve it. For example, a simple example is: syms ...

9 dagen ago | 1

| accepted

Answered
Double integration of a binomial function (in x and y) generated from two row arrays
Let me explain, because you either have a simple problem to solve, or an impossible one. I've restated my comment as an answer,...

9 dagen ago | 1

Answered
cubic interpolation vs spline interpolation vs cubic spline interpolation?
pchip is not a true cubic spline, in the sense that it is not a twice differentiable piecewise cubic interpolant. pchip is only ...

9 dagen ago | 0

Answered
F solve error, how can I fix it?
There are no real solutions. First, I converted them to a problem that fimplicit can use. F1 = @(x,y) -(118/121)*x.^2-(333/242)...

9 dagen ago | 0

Answered
find least squares parameters
Did you try polyfit? If not, then do so.

10 dagen ago | 0

Answered
how to do the equation following its answer on matlab?
There is the obvious... Using y = 1/z, we can transform the problem. syms z y Fz = (1/z + 1/z^2 - 1/z^3)/(1 + 1/z + 1/z^2 + 4...

10 dagen ago | 0

| accepted

Answered
Got an Error Using Grid -Unknown Command Option
You don't get charged less for MATLAB, if you save on lines of code. They also don't charge less if you use another comma. You ...

10 dagen ago | 0

Answered
why the result of the following code vector y is not equals to y1 or y2 . How can I get the equals of them.
y2 y2 = 3414.6226519281 3421.81651603882 3493.03577073497 3510.3010446007 ...

11 dagen ago | 1

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