John D'Errico
Retired
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Inverting an 8x8 symbolic matrix
What nobody ever seems to understand is that a symbolic inverse of a matrix like this grows exponentially in complexity. Many th...
Inverting an 8x8 symbolic matrix
What nobody ever seems to understand is that a symbolic inverse of a matrix like this grows exponentially in complexity. Many th...
15 hours 前 | 3
已回答
Is there any precomputation step on A'*(.)*A if matrix A is known, to speed up matrix computation A'*B_i*A in matlab with B_i denpends on the previous matrix B_{i-1}.
A is known and fixed, and apparently large, else you would not care about speed. The amount of memory on your laptop is irrelev...
Is there any precomputation step on A'*(.)*A if matrix A is known, to speed up matrix computation A'*B_i*A in matlab with B_i denpends on the previous matrix B_{i-1}.
A is known and fixed, and apparently large, else you would not care about speed. The amount of memory on your laptop is irrelev...
2 days 前 | 0
已回答
How to identify algorithm time complexity?
It is not at all trivial to determine the time complexity for SOME algorithms, at least not from merely knowing the method emplo...
How to identify algorithm time complexity?
It is not at all trivial to determine the time complexity for SOME algorithms, at least not from merely knowing the method emplo...
2 days 前 | 0
已回答
Where to Find a Dataset of High-Quality MATLAB Code for Training an LLM?
Looking at your question a second time, it is about MATLAB in a sense. in that you are looking for a repository of code to train...
Where to Find a Dataset of High-Quality MATLAB Code for Training an LLM?
Looking at your question a second time, it is about MATLAB in a sense. in that you are looking for a repository of code to train...
5 days 前 | 0
已回答
Logic Code required to be run in finite time
I think you misunderstand an important idea of computing. You NEVER want to use brute force on big problems. Those problems alwa...
Logic Code required to be run in finite time
I think you misunderstand an important idea of computing. You NEVER want to use brute force on big problems. Those problems alwa...
9 days 前 | 1
已回答
Find blocks iof non-zero values in Matrix
Sure. It should even be pretty easy. A = randi(200,[120,240]); % make up a matrix First, I'll convert it to binary, where a 1 ...
Find blocks iof non-zero values in Matrix
Sure. It should even be pretty easy. A = randi(200,[120,240]); % make up a matrix First, I'll convert it to binary, where a 1 ...
13 days 前 | 0
已回答
assigning values with []
@feynman feynman The funny thing is, I have at times wanted a syntax like you wrote to work in MATLAB, but it won't. We could p...
assigning values with []
@feynman feynman The funny thing is, I have at times wanted a syntax like you wrote to work in MATLAB, but it won't. We could p...
14 days 前 | 1
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已回答
How would I use a 2D array based on a topographical map to determine the steepest direction at each point?
You should be talking to your teacher, as these are questions they should be answering. But what does the gradient function do? ...
How would I use a 2D array based on a topographical map to determine the steepest direction at each point?
You should be talking to your teacher, as these are questions they should be answering. But what does the gradient function do? ...
16 days 前 | 1
| 已接受
已回答
Solving odes with ode45 and then checking fixed points for constant behavior,
How many times will you ask this question? Can you do better than 13-14 digits? No. Not in double precision. And a different O...
Solving odes with ode45 and then checking fixed points for constant behavior,
How many times will you ask this question? Can you do better than 13-14 digits? No. Not in double precision. And a different O...
17 days 前 | 0
| 已接受
已回答
I have a dataset of x and y coordinates in UTM units, and cumulative erosion or sedimentation in depth (m) units, I need the volume of erosion or accretion in cubic metres
Difficult, since you don't show the data. A picture of numbers is useless. A bigger problem is your data is surely not on some n...
I have a dataset of x and y coordinates in UTM units, and cumulative erosion or sedimentation in depth (m) units, I need the volume of erosion or accretion in cubic metres
Difficult, since you don't show the data. A picture of numbers is useless. A bigger problem is your data is surely not on some n...
21 days 前 | 0
已回答
In a (possibly directed) graph, is there a simple way to find all nodes reachable for a given node?
First, create a graph. M = eye(100) + triu(rand(100) < 0.035); spy(M) You will agree this matrix satisfies the requirements, ...
In a (possibly directed) graph, is there a simple way to find all nodes reachable for a given node?
First, create a graph. M = eye(100) + triu(rand(100) < 0.035); spy(M) You will agree this matrix satisfies the requirements, ...
21 days 前 | 0
| 已接受
已回答
Evaluating stability of fixed points in a system of differential equations,
First, there is nothing wrong with a loop! You know how to evaluate stability for each case. Just write the loop. Could you do s...
Evaluating stability of fixed points in a system of differential equations,
First, there is nothing wrong with a loop! You know how to evaluate stability for each case. Just write the loop. Could you do s...
24 days 前 | 0
| 已接受
已回答
linprog
Think about it. Do you need that constant at all? (NO.) LINPROG finds a location (in your case, in terms of x and y) that minim...
linprog
Think about it. Do you need that constant at all? (NO.) LINPROG finds a location (in your case, in terms of x and y) that minim...
24 days 前 | 0
已回答
how to design digital filter
Are there free toolboxes to do filter design? You might find something on the file exchange, and what you find there comes at ...
how to design digital filter
Are there free toolboxes to do filter design? You might find something on the file exchange, and what you find there comes at ...
1 month 前 | 0
已回答
why does this not work?
It failed because datetime did not recognize that string as a list of distinct times. Just because you know what you want code t...
why does this not work?
It failed because datetime did not recognize that string as a list of distinct times. Just because you know what you want code t...
1 month 前 | 3
已回答
Solving for a variable in an equation
First, you need to recognize there is NO analytical solution to your problem. So using solve means it will just toss and turn fo...
Solving for a variable in an equation
First, you need to recognize there is NO analytical solution to your problem. So using solve means it will just toss and turn fo...
1 month 前 | 0
已回答
Does inverse modelling is possible with ANFIS?
In general, absolutely no. This is impossible. Why do I say that? Consider even an absolutely trivial linear model. I don't need...
Does inverse modelling is possible with ANFIS?
In general, absolutely no. This is impossible. Why do I say that? Consider even an absolutely trivial linear model. I don't need...
1 month 前 | 0
| 已接受
已回答
Why is vpa not converting double accurately?
Quite interesting. When I first saw the title, I assumed it would be an obvious mistake. Then I saw the poster, and knew it woul...
Why is vpa not converting double accurately?
Quite interesting. When I first saw the title, I assumed it would be an obvious mistake. Then I saw the poster, and knew it woul...
1 month 前 | 1
| 已接受
已回答
finding partial solutions from ill-conditioned equations
The largest subset? It may be impossible to compute ANY subset accurately. You may be able to only compute a linear combination ...
finding partial solutions from ill-conditioned equations
The largest subset? It may be impossible to compute ANY subset accurately. You may be able to only compute a linear combination ...
1 month 前 | 0
已回答
What is evaluated to standard output is not being assigned to my variable
This is a not uncommon misunderstanding about cell arrays. d = {'.'; '..' '2022' '2024' '2025'} b = d(3:end) % the "righ...
What is evaluated to standard output is not being assigned to my variable
This is a not uncommon misunderstanding about cell arrays. d = {'.'; '..' '2022' '2024' '2025'} b = d(3:end) % the "righ...
1 month 前 | 1
| 已接受
已回答
Create similar curves through specific data points
The question is becoming more clear now, based on your response to my first answer. I'll post this as a separate answer, since t...
Create similar curves through specific data points
The question is becoming more clear now, based on your response to my first answer. I'll post this as a separate answer, since t...
2 months 前 | 0
| 已接受
已回答
Create similar curves through specific data points
You have asked a confusing question, which usually means you are yourself confused, perhaps about what you really want to do. It...
Create similar curves through specific data points
You have asked a confusing question, which usually means you are yourself confused, perhaps about what you really want to do. It...
2 months 前 | 0
已回答
Solving linear system modulo prime^n when matrix is univertable
You can't use LU anyway, since it is not designed to work on that problem. Nor can you use slash or backslash, which again, do n...
Solving linear system modulo prime^n when matrix is univertable
You can't use LU anyway, since it is not designed to work on that problem. Nor can you use slash or backslash, which again, do n...
2 months 前 | 0
已回答
Differentiating inside a matlab function
Oh, you were so close. Actually, you did not even need to tell diff what variable to differentiate with respect to. syms x(t) ...
Differentiating inside a matlab function
Oh, you were so close. Actually, you did not even need to tell diff what variable to differentiate with respect to. syms x(t) ...
2 months 前 | 0
已回答
How to generate an prime random number??
A random prime? Impossible to do. That is, something that many seem to misunderstand is you cannot generate a random number on s...
How to generate an prime random number??
A random prime? Impossible to do. That is, something that many seem to misunderstand is you cannot generate a random number on s...
2 months 前 | 0
已回答
How to make multiple lines of best fit into one scatter graph
Is it possible to do in MATLAB? Of course it is. It of course depends on the skill of the person writing the code. It depends on...
How to make multiple lines of best fit into one scatter graph
Is it possible to do in MATLAB? Of course it is. It of course depends on the skill of the person writing the code. It depends on...
2 months 前 | 0
已回答
Find best fit curve from multiple curves of different size
On the right end, you have an infinite slope. On the left end, not so much of a problem. But it will be better to do a couple of...
Find best fit curve from multiple curves of different size
On the right end, you have an infinite slope. On the left end, not so much of a problem. But it will be better to do a couple of...
2 months 前 | 0
已回答
How does interp1 work?
Why not post the actual data you used that caused the problem, instead of only a tiny fragment of it? You certainly CAN post t...
How does interp1 work?
Why not post the actual data you used that caused the problem, instead of only a tiny fragment of it? You certainly CAN post t...
2 months 前 | 2
已回答
Matlab Dimpulse function documentaion not found
It seems dimpulse (or at least one version thereof) can be found in the control TB. which dimpulse -all However, given the loc...
Matlab Dimpulse function documentaion not found
It seems dimpulse (or at least one version thereof) can be found in the control TB. which dimpulse -all However, given the loc...
2 months 前 | 0
已回答
part 3 example was wrong
Answers is not official MATLAB support. So telling us a problem exists does nothing. Contact support directly. https://www.ma...
part 3 example was wrong
Answers is not official MATLAB support. So telling us a problem exists does nothing. Contact support directly. https://www.ma...
2 months 前 | 1
