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John D'Errico


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5,139 2006 年以降の合計貢献数

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

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Fitting an exponential using nlinfit
Most of the code you posted is meaningless, since you save only the variables whos Name Size Bytes ...

約5時間 前 | 0

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random integer condition selection
You want to generate a random number of random numbers? With an additional constraint that all are greater than 0.5? This is far...

約11時間 前 | 1

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[Solved] Upsampling multidimensional array with interpn
That is NOT a 5 dimensional array. While you may THINK of it as a set of points that live in 5 dimensions, it is NOT a 5-d arra...

約23時間 前 | 0

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Plotting a function (Horner Schema)
While polynomic psychological analysis seems well beyond my talents, Horner's rule is pretty easy. :) And since you made a credi...

1日 前 | 1

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Matlab says the matrix is not symmetric
D = rand(100); D = (D + D.')/2; issymmetric(D) ans = logical 1

1日 前 | 1

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how can i create a circle with a face color changing radially
[x,y] = meshgrid(linspace(-3,3)); z = exp(-x.^2 - y.^2); H = pcolor(z); H.LineStyle = 'none'; colormap(jet) axis equal ...

1日 前 | 0

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Fit a curve on scatter data (main behaviuor)
You "want" the green line. I want the Buffalo Bills to win the Super bowl. Probably not gonna happen in either case. ;-) You wa...

1日 前 | 0

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How can I understand why certain sets of random variates lead to the warning message "Unable to meet integration tolerances without reducing the step size below the smallest value allowed (1.136868e-13) at time t=51"?
Nobody yet wants to explain it? The standard reason for this error is because you are creating a problem that is too stiff for ...

1日 前 | 2

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What am I getting wrong with trying to create a sphere mesh using a golden spiral?
So you are not looking for a mesh at all, just a uniform sampling? Simplest might be to use a random sampling, with a twist. Tha...

2日 前 | 0

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Why do I get a graph that is symmetrical based on x=-2 when I draw a graph of y1=4*log((x+2))?
It is not clear what you wanted to plot. However, I think you misunderstand. It is still possible to evaluate the log of a nega...

3日 前 | 0

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Tabulated Gauss-Kronrod weights and abscissae
I might presume the mp indicates some variation of the multi-precision toolbox. An old free version has been on the File Exchang...

4日 前 | 0

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Solving symbolic trig equation
You can NEVER solve for those variables, at least as the equations are written. First of all, z never even appears. But since y...

4日 前 | 1

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How to get the value of an extra variable with fsolve
The simple trick is to use the output arguments from a function. Change your function header to look like this: function [F,r...

4日 前 | 0

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Find the intersection points between two data sets
Finding the intersection point is easy enough. [intx,inty] = intersections(data1(:,1),data1(:,2),data2(:,1),data2(:,2)) intx =...

4日 前 | 1

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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...

5日 前 | 1

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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...

5日 前 | 0

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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...

6日 前 | 1

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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...

6日 前 | 1

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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...

7日 前 | 0

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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...

7日 前 | 0

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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,...

7日 前 | 2

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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...

7日 前 | 1

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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...

9日 前 | 0

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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...

9日 前 | 0

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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...

9日 前 | 0

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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...

9日 前 | 0

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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 ...

11日 前 | 1

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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 ...

11日 前 | 0

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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...

11日 前 | 0

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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...

12日 前 | 0

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