
John D'Errico
Retired
A retired applied mathematician, consultant, sometime mechanical engineer, numerical analyst, woodworker, bridge player. Please DON'T contact me, as too many students then decide I am their personal consultant if I allow it. I won't do consulting by mail.
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How to make change in the algorithm to start and end at a same point?
Your problem is, you want to force the code to return a tour that starts at point 1, and ends there. And that is where you are W...
How to make change in the algorithm to start and end at a same point?
Your problem is, you want to force the code to return a tour that starts at point 1, and ends there. And that is where you are W...
2日 前 | 0
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Converting from syms to double
We don't see what is in that variable. But... If you cannot convert it to a double, then it is not a number. It has some symbol...
Converting from syms to double
We don't see what is in that variable. But... If you cannot convert it to a double, then it is not a number. It has some symbol...
2日 前 | 0
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different time executions........
And you are surprised, because? Did you xpect exactly the same amount of time taken, EVERY TIME, to within a millisecond? Yes,...
different time executions........
And you are surprised, because? Did you xpect exactly the same amount of time taken, EVERY TIME, to within a millisecond? Yes,...
2日 前 | 0
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ExB drift velocity code equation
I might guess that what you really want is to divide by the square of the norm of B. NOT by the elements of B squared. E = 0.1;...
ExB drift velocity code equation
I might guess that what you really want is to divide by the square of the norm of B. NOT by the elements of B squared. E = 0.1;...
3日 前 | 0
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why did the "text" function stop working while creating a new section in my live data
Whenever a function "stops working" you need to see if you have created a variable named text, or another function or script by ...
why did the "text" function stop working while creating a new section in my live data
Whenever a function "stops working" you need to see if you have created a variable named text, or another function or script by ...
5日 前 | 0
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How to solve this equation?
As I see it, from your question, I think people have been missing the point. As has been said, there are no real solutions for s...
How to solve this equation?
As I see it, from your question, I think people have been missing the point. As has been said, there are no real solutions for s...
6日 前 | 2
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How to solve out of memory error when constructing sparse matrix
Remember that i and j and v also take memory. (222263280*4*2 + 222263280*8)/1024^3 So those three variables alone require 3.3 ...
How to solve out of memory error when constructing sparse matrix
Remember that i and j and v also take memory. (222263280*4*2 + 222263280*8)/1024^3 So those three variables alone require 3.3 ...
6日 前 | 0
回答済み
What is 5A?
The obvious seems clear, since I recall arithmetic. FiveA = [15 10 25 5]; I think you DESPERATELY NEED to do the basic Onramp ...
What is 5A?
The obvious seems clear, since I recall arithmetic. FiveA = [15 10 25 5]; I think you DESPERATELY NEED to do the basic Onramp ...
7日 前 | 0
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Find the volume of the solid generated by revolving about the x-axis the region bounded by the curve y= 4/x^2+4,the axis, and the lines x=0 x=2
The question is now a year old, so I'll show how to solve it. @Mukesh chose to work with a different domain than the question as...
Find the volume of the solid generated by revolving about the x-axis the region bounded by the curve y= 4/x^2+4,the axis, and the lines x=0 x=2
The question is now a year old, so I'll show how to solve it. @Mukesh chose to work with a different domain than the question as...
8日 前 | 0
回答済み
Matlab simulation for projectile motion
I think I don't understand their not understanding. (Ok, that seems confusing even to me, and I wrote it.) I would just write i...
Matlab simulation for projectile motion
I think I don't understand their not understanding. (Ok, that seems confusing even to me, and I wrote it.) I would just write i...
9日 前 | 0
回答済み
Remove algebraic loop without delay
I don't know for sure how Simulink resolves the issue internally, but the answer seems straightforward. Consider the equation ...
Remove algebraic loop without delay
I don't know for sure how Simulink resolves the issue internally, but the answer seems straightforward. Consider the equation ...
12日 前 | 0
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Mathematical functions across variables
Is there a good reason why you would not just try this? A(1,1) + B(2,1) I think you are coming from a spreadsheet world. And f...
Mathematical functions across variables
Is there a good reason why you would not just try this? A(1,1) + B(2,1) I think you are coming from a spreadsheet world. And f...
12日 前 | 0
回答済み
Draw samples using a Non-Gaussian distribution
I think you don't understand random numbers, AND you don't understand indexing in MATLAB. What does this do? random('poisson',1...
Draw samples using a Non-Gaussian distribution
I think you don't understand random numbers, AND you don't understand indexing in MATLAB. What does this do? random('poisson',1...
12日 前 | 0
回答済み
how does fmincon deal with ill-conditioned problem?
fmincon assumes you know what you are doing. (Is that not a good idea?) It tries to solve what you gave it to solve. Surely that...
how does fmincon deal with ill-conditioned problem?
fmincon assumes you know what you are doing. (Is that not a good idea?) It tries to solve what you gave it to solve. Surely that...
14日 前 | 0
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Sub-optimal curve fitting, cannot find asymptotic value
I think you do not understand. Estimating an asymptote from data is a problem of extrapolation. It will be strongly dependent on...
Sub-optimal curve fitting, cannot find asymptotic value
I think you do not understand. Estimating an asymptote from data is a problem of extrapolation. It will be strongly dependent on...
16日 前 | 0
回答済み
unbounded in linear programming
First, read the warning message! "Warning: Length of lower bounds is < length(x); filling in missing lower bounds with -Inf." ...
unbounded in linear programming
First, read the warning message! "Warning: Length of lower bounds is < length(x); filling in missing lower bounds with -Inf." ...
16日 前 | 0
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Problem 2022. Find a Pythagorean triple
A simple enough solution... isTherePythagoreanTriple(1,2,3,4) isTherePythagoreanTriple(3,4,5,6) isTherePythagoreanTriple(12,1...
Problem 2022. Find a Pythagorean triple
A simple enough solution... isTherePythagoreanTriple(1,2,3,4) isTherePythagoreanTriple(3,4,5,6) isTherePythagoreanTriple(12,1...
17日 前 | 0
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I don't know why you're saying it's an invalid expression. Help me
You NEED to learn about the dotted operators, thus .*, ./, and .^ operators. When x is a vector, for example, this: x = 1:5 ...
I don't know why you're saying it's an invalid expression. Help me
You NEED to learn about the dotted operators, thus .*, ./, and .^ operators. When x is a vector, for example, this: x = 1:5 ...
18日 前 | 0
回答済み
How can I simplify the symbolic expressions?
clear clc syms q_bar delta_o theta1 theta2 q S CL_alpha CL_delta b e KT eqn1 = (2*theta1 - theta2 - q_bar.*theta1 + q_bar.*th...
How can I simplify the symbolic expressions?
clear clc syms q_bar delta_o theta1 theta2 q S CL_alpha CL_delta b e KT eqn1 = (2*theta1 - theta2 - q_bar.*theta1 + q_bar.*th...
19日 前 | 0
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series computing is faster than parallel computing using parfor
There is no assurance that a parallel code will be faster than any specific serial code. ABSOLUTELY NONE. In fact, I can easily ...
series computing is faster than parallel computing using parfor
There is no assurance that a parallel code will be faster than any specific serial code. ABSOLUTELY NONE. In fact, I can easily ...
20日 前 | 0
回答済み
Elevar un polinomio al cuadrado
Easy enough. g = [3/2 -1/4 -1/3]; gsym = poly2sym(g); gsym^2 And as you know, it squares the polynomial, but does not expand...
Elevar un polinomio al cuadrado
Easy enough. g = [3/2 -1/4 -1/3]; gsym = poly2sym(g); gsym^2 And as you know, it squares the polynomial, but does not expand...
21日 前 | 0
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Optimization of a matrix with integers with nonlinear objective functions and nonlinear constraints
You are correct, in that fmincon does not provide integer constraints as an option, and that a tool like intlinprog does not all...
Optimization of a matrix with integers with nonlinear objective functions and nonlinear constraints
You are correct, in that fmincon does not provide integer constraints as an option, and that a tool like intlinprog does not all...
21日 前 | 0
回答済み
Newton Raphson Method: while loop
There are many, MANY ways to stop a while loop. For example... tol = 1e-8; err = inf; iter = 0; itmax = 100; while (abs(err...
Newton Raphson Method: while loop
There are many, MANY ways to stop a while loop. For example... tol = 1e-8; err = inf; iter = 0; itmax = 100; while (abs(err...
21日 前 | 0
回答済み
Best way to count outputs for a 2D polynomial function along the curve of an implicit equation
Um, good luck at doing it at all well. Even anything in the right ball park would be a success. But you won't know how well you ...
Best way to count outputs for a 2D polynomial function along the curve of an implicit equation
Um, good luck at doing it at all well. Even anything in the right ball park would be a success. But you won't know how well you ...
22日 前 | 0
回答済み
Different Nonlinear Equality and Inequality Constraint Tolerances
As @Torsten said, the answer is a simple one. No. But sometimes, no can be a fuzzy word. :-) For example, suppose I have two co...
Different Nonlinear Equality and Inequality Constraint Tolerances
As @Torsten said, the answer is a simple one. No. But sometimes, no can be a fuzzy word. :-) For example, suppose I have two co...
22日 前 | 1
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Converging on local minima using ga(). Ways to increase odds of finding global minima.
So big problems take time. Should this be a surprise? More time invested can be a gain, since here it will improve the ability o...
Converging on local minima using ga(). Ways to increase odds of finding global minima.
So big problems take time. Should this be a surprise? More time invested can be a gain, since here it will improve the ability o...
22日 前 | 1
回答済み
Name of islocalmin algorithm
You can read about it here: islocalmin But is there a specific "algorithm" that can be named? It seems a pretty simple algorit...
Name of islocalmin algorithm
You can read about it here: islocalmin But is there a specific "algorithm" that can be named? It seems a pretty simple algorit...
23日 前 | 0
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Detrending still leaves a slope
It depends on how you define detrend. Clearly, you have a different definition from me, at least, as well as the author of the f...
Detrending still leaves a slope
It depends on how you define detrend. Clearly, you have a different definition from me, at least, as well as the author of the f...
23日 前 | 1
回答済み
Operator '*' is not supported for operands of type 'function_handle'.
Too many errors in this code to list them all out. Starting at the beginning... eta_0 = 1 % Initial value of eta That line doe...
Operator '*' is not supported for operands of type 'function_handle'.
Too many errors in this code to list them all out. Starting at the beginning... eta_0 = 1 % Initial value of eta That line doe...
23日 前 | 1
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Why does it take MATLAB so long to print hello world?
To me, this all seems to be making a mountain out of a mole hill. Yes, if you are going to launch MATLAB, even with no gui inte...
Why does it take MATLAB so long to print hello world?
To me, this all seems to be making a mountain out of a mole hill. Yes, if you are going to launch MATLAB, even with no gui inte...
24日 前 | 0