Answered
Hi, I'm writing a Runge Kutta function to solve a higher order differential equation and I need to get the error to around 10^-11.
You need to rewrite your derivative function as a vector function to account for the higher order derivatives. You've got a 4x1...

9 years ago | 1

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Answered
Multiply Each Matrix in Cell Array by a Different Value
result = cellfun(@times,A,num2cell(b),'uni',false); But this just moves the loops (which are part of cellfun) into the back...

9 years ago | 1

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Answered
create binary 0 and 1
subA = A(sum(A,2)==3,:); For subB it is not entirely clear to me what you want. Do you want the rows of A arranged so that...

9 years ago | 0

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Answered
sort from largest to smallest
sort(A(:,1),'descend') If you want to sort the matrix A by rows based on the first column, then e.g. flipud(sortrows(A...

9 years ago | 2

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Answered
increasing spdiags matrix at each iteration
A2 = repmat(A2,1,i); But it seems to me that you may be running into memory problems with this, since A2 is recursively usi...

9 years ago | 0

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Write a function called approximate_e that uses the following formula to compute e, Euler’s number: = 1 ! ∞ = 1+1+ 1 2 + 1 6 + 1 24 +⋯ Instead of going to infinity, the function stops at the smallest k for which the approximation differs from
You need to change your while loop criteria to compare your estimate with exp(1). E.g., while abs(est-exp(1)) > delta

9 years ago | 0

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Answered
how do i select a number from a set randomly
If you are just interested in the values -1 and 1, you could do something like this: Asimulac = round(rand(101,5))*2-1; ...

9 years ago | 0

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Problems with simulation of Earth-Moon trajectories around the Sun
I haven't looked at your derivative equations yet, but the order is definitely wrong. E.g., take the first two elements: i...

9 years ago | 0

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Answered
Reverse the value in multiple columns
x = your matrix c = a vector with column numbers to reverse x(:,c) = 6 - x(:,c); e.g., >> x = randi(5,6,6) % <-...

9 years ago | 0

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How to plus two nan matrix
c = a + b; c(isnan(c)) = a(isnan(c)); c(isnan(c)) = b(isnan(c));

9 years ago | 1

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Answered
How do I make a function file that can calculate the modified eulers method?
For Modified Euler's Method, you simply average the derivative at your initial point and next point, and then use that to take a...

9 years ago | 0

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how to cut the matrix
x = [1 0.1 2 0.2 3 0.3 4 0.5 5 0.6 6 1.2 7 1.2 8 1.3]; >> y = x(x(:,2)<1.2,:) y = 1.0000 ...

9 years ago | 0

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Answered
Help with creating a modified Euler method for a bungee jumping question
For Modified Euler's Method, e.g. this link: https://mat.iitm.ac.in/home/sryedida/public_html/caimna/ode/euler/ie.html Bas...

9 years ago | 0

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Which standard MATLAB functions do you shadow with your own version, and why?
I have intentionally shadowed fopen, fread, fwrite, fclose before. Options that would read/write VAX binary format numbers were...

9 years ago | 3

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I have 100 2D matrix .. After each matrix, I calculate the sum of elements inside it .. I want to see only the matrices with summation result under certain value (such as: 23). How can I do this?
E.g., if they were stored in a 3D array: >> m = randi(10,3,3,5) % some random data m(:,:,1) = 5 8 7 ...

9 years ago | 0

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Anyone know what I am getting this error?
Use the debugger. First, type the following: dbstop if error Then run your code. When the error occurs, the program wi...

9 years ago | 1

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Incorrect number of arguments into mex file
Particularly for Fortran, you should always use the exact signature that is in the doc. Sometimes that signature changes from r...

9 years ago | 1

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Answered
What if I find an error in the documentation
Go to this link: https://www.mathworks.com/support/bugreports/ Click on the green "Report a Bug" near the top right, and g...

9 years ago | 0

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Answered
Accessing an array that is singles which is part of a structure is really slow
Timings like this are inherently unreliable. The actual operations involved are extremely simple, so the runtimes can easily be...

9 years ago | 0

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I am trying to plot within a for loop, but it is only plotting the last set of data. How would I get all three sets of data in the same graph. The code is included
Change hold off to hold on Also, I assume those labels and title were meant to be on the plot, not set as actua...

9 years ago | 0

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Random path coordinates in 2D within a unit square
Any restrictions on the path? E.g., would 1000 random points suffice: mypath = rand(1000,2); % <-- each row is an (x,y) p...

9 years ago | 0

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How to quary (building a new matrix based on some information)
C = B(ismember(B(:,1),A(:,1)),:); D = C(C(:,2)==1,:);

9 years ago | 0

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how to assign different value for each input
Not quite sure what you really want, but here is a start: ci = [0.9 0.95 0.99 0.999]; c = [1.645 1.960 2.576 3.291]; ...

9 years ago | 0

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How do I combine matrices of different dimensions which are obtained in a for loop?
Do you mean something like this? result = zeros(10,11); for k=1:10 result(k,1:k+1) = 1:k+1; % or whatever the co...

9 years ago | 0

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Error is compiling mex file in MATLAB with intel compiler "Intel Visual Fortran Composer XE 2013 with Microsoft Visual Studio 2010"
For a fixed format source file, the continuation line must have the continuation character in column 6. You have several lines ...

9 years ago | 0

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Further improvement of matrix inversion
_How can we further speed up this inversion if we know from the beginning that Cholesky decomposition can apply in our matrix?...

9 years ago | 1

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Answered
Why can't Mex C/C++ Code With Xcode on Mac (MatlabR2015a)?
There are no spaces between the directive and the token. So change these lines #ifndef_DOUBLEIT_H_ #define_DOUBLEIT_H_ ...

9 years ago | 0

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Answered
How to merge matrices generated from a for loop into one matrix.
E.g., as a matrix of columns: solutionV = zeros(___,numel(k)); % <-- fill this in to pre-allocate : solutionV(...

9 years ago | 0

Answered
I'm coding a Connect4 game. Firstmove should play bottom middle of an empty board if I am first, secondmove should play to the left or right of the other player if I am second. Why does my code play bottom middle and to the left of my own move?
Several problems: Replace this line: if state == zeros(6,7) with this to test for matrix equality: if isequa...

9 years ago | 0

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Answered
What is wrong with my code? Cycle while help
You need to break out of the loop when you hit the bottom corner. Also, you need to add in code that updates m and/or n as you ...

9 years ago | 1

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