John D'Errico
Last seen: Today
Retired
5,456 total contributions since 2006(Don't contact me. I won't answer questions.) A retired mathematician, numerical animalist, woodworker, bridge player.
John D'Errico's Badges
Answer 50 questions that were unanswered for more than 30 days
Awarded to John D'Errico on 15 Nov 2020
Contribute at least one answer each month for 36 consecutive months
Awarded to John D'Errico on 20 Jul 2017
Obtain 50 solvers for a problem you have created
Awarded to John D'Errico on 10 Sep 2020
Like a problem or solution
Awarded to John D'Errico on 13 Oct 2016
Be the first to solve a problem
Awarded to John D'Errico on 28 Aug 2016
Top ten contributors with the most downloaded submissions
Awarded to John D'Errico on 02 Jan 2020
Your submissions were downloaded 1000 or more times in a month
Awarded to John D'Errico on 01 Nov 2019
Your submission is selected as "Pick of The Week"
Awarded to John D'Errico on 09 Oct 2019
Publish your first comment or rating
Awarded to John D'Errico on 09 Oct 2019
Your submissions received 25 five star ratings
Awarded to John D'Errico on 09 Oct 2019
Publish your first submission
Awarded to John D'Errico on 09 Oct 2019
Accept 50 answers given by other contributors
Awarded to John D'Errico on 20 Jul 2017
100 of your answers have been accepted
Awarded to John D'Errico on 20 Jul 2017
Provide your first answer ever to someone else's question
Awarded to John D'Errico on 20 Jul 2017
How can I fit an exponential curve?
x = [35.668 34.448 33.317 30.357 27.598]; y = [180 504 1260 10300 80900]; plot(x,y,'o-') First, recognize you have only 5 ...
8 hours ago | 0
| accepted
Calculation of two less than equal
You want to solve for a scalar m such that the inequalities are always true? Regardless, does a solution ever exist? Note that u...
14 hours ago | 1
i am new. i need help. kindly answer.
If this is homework? It very possibly is, because there are relatively few good reasons I can think of to solve any integration ...
15 hours ago | 2
Euler's Method and exact solution plot
Sorry, but your code is wrong (so is your exact solution.) Why? Look at what you wrote. h=0.05; % time step t=...
3 days ago | 1
MATLAB cannot integrate trigonometry in the form of degree
I think you do not understand integration, IF your expectation really is the two should be the same. That is, you think the inte...
3 days ago | 1
how to plot a function symbolically?
You have the relationship z(r) = H - C^2/(2*g*r^2) If H and C are not known, with g fixed at 9.8, then they make this in...
3 days ago | 0
Query regarding finding the index which will give 90% of the total area under the curve
No. You found some approximations of the area, using either trapz or polyarea. In both cases, they produced what is a trapezoida...
3 days ago | 1
fit these curves and what type of fit they are?
Your data is noisy. There is NO specific function that describes the data. It is NOT truly linear. It is NOT truly exponential, ...
3 days ago | 0
| accepted
I want to set a range of variable to three or four places of decimals
Are you asking to create a variable that only carries 3 or 4 digits of precision? You can't choose to set an arbitrary precision...
3 days ago | 0
atan2 not consisent
What you don't understand is that just because MATLAB displays a number represented to 15 digits, does not mean it is EXACTLY th...
4 days ago | 0
Error using ==> asind Argument should be real.
So what is the problem? It seems the error message states exactly what happened, and why MATLAB sees a problem. Honestly, it ju...
5 days ago | 1
| accepted
how do I right x^2 in MATLAB
Is x a scalar? If so, then you write it as x^2. Is x a vector? Then, assuming you want to perform an element-wise squaring, yo...
5 days ago | 0
| accepted
4D Interpolation scattered Data
Sorry, but you cannot use tools like griddata or scatteredInterpolant to interpolate non-single valued relations. It seems all y...
5 days ago | 0
How to draw a 3D circle that is tangent to two lines
First, if the lines are in the same plane, then you can pretend this is a problem in 2-dimensions. You can always rotate everyth...
5 days ago | 0
| accepted
Determinant of a unitary matrix
Gosh. I wonder, if there were really much better ways to compute the determinant, they might have used it? ;-) There are no spe...
5 days ago | 0
| accepted
How to remove duplicates from a matrix without using unique?
How could you use the output of a sort to help? Why not make an effort?
6 days ago | 1
Can anyone tell what is this line doing
You asked again, why you cannot use f(1,3), instead of f(1,2). LOOK CAREFULLY AT WHAT YOU HAVE. TAKE IT ONE STEP AT A TIME. f...
6 days ago | 0
| accepted
Create Random Points in Elliptical Belt
If you already know how to generate random points uniformly over an elliptical region, then you already have the simple answer. ...
6 days ago | 0
| accepted
Exponential distributed random values
You need to do that since your exponential rate parameter varies. If it were constant, this would not be necessary. The first a...
6 days ago | 0
| accepted
How can I solve the determinant of large-sized symbolic matrix: det(A)=0?
First, you don't want to solve for a zero determinant! Period. This will never be a well-posed problem, simply because we can tr...
7 days ago | 0
| accepted
Composite Simpson's 1/3 rule code error
Tell me, what is fx? fx is NOT a function. It is a scalar, vector, or array. Whatever x was, fx is the same thing. If it NOT a ...
7 days ago | 0
excluding a small combinations from a combination?
There are not that many combinations that include the subset [2 4 6] out of nchoosek(1:10,4). This means the oversampling will n...
7 days ago | 0
How to plot a complex function in matlab like : f(z)=sin(z)?
The problem is, if z is a complex variable, then so is the extension of sin(z) into the complex plane. For example... sin(1 + i...
8 days ago | 1
Integration of a function
It can be confusing at times I have seen for newcomers to know which tools apply where, because we have symbolic tools and numer...
8 days ago | 0
| accepted
what does this line do
It does nothing on its own. A single line of code has little meaning, out of context. What does it do? It sets some elements o...
8 days ago | 0
Matlab solver for natural log equation
Does a solution near(er) to zero exist? PLOT IT!!!!!! syms x f = (-27109/x)-0.95*log(x)+25.18 - log(0.5); fplot(f,[10,1000]) ...
8 days ago | 0
| accepted
Is NaN ok here?
Sure. It does not bother me. Why does it bother you? B = [1.66000000e-01 6.60000000e-02 1.40000000e-02 3.90000000e-02 1.4000000...
9 days ago | 0
| accepted
Gaussian Quadrature Error Help
I think you misiunderstand Gaussian quadrature. You claim to have 4 points. WRONG. You have TWO points in x, and TWO in y, the...
10 days ago | 1
| accepted
Tic, Toc Behavior
Using tic and toc to masure any time is a bad idea. Using tic and toc to masure any time is a bad idea. Using tic and toc to m...
10 days ago | 1
Select a Web Site
Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select: .
Select web siteYou can also select a web site from the following list:
Americas
- América Latina (Español)
- Canada (English)
- United States (English)
Europe
- Belgium (English)
- Denmark (English)
- Deutschland (Deutsch)
- España (Español)
- Finland (English)
- France (Français)
- Ireland (English)
- Italia (Italiano)
- Luxembourg (English)
- Netherlands (English)
- Norway (English)
- Österreich (Deutsch)
- Portugal (English)
- Sweden (English)
- Switzerland
- United Kingdom (English)