How do I save values in my loop as a column vector?

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Francesca Maher
Francesca Maher 2020-3-30
评论： Francesca Maher 2020-3-30
I have a loop and I need to save two values (h and err_max) from it into a column vector so that I can make a table. I have been using ' after the variable to transpose the vector so that my table works, but this sometimes causes issues when running the whole file because of other sections i have written. Is there a way to save values from a loop into a column vector without using '?
Side note: My value sol2 saves as a column vector by using sol2(k, : ) but I have tried this on h and it creates a big matrix instead.
I will copy my code here:
for i = 1:16
h = 2^-(i+1);
N = 4/h;
% Initialise variables
k = 0;
sol2 = 0;
for t = 0:h:4
k = k + 1;
sol2(k,:) = 2*(t) - exp(t);
end
w=Euler(a,b,N,alpha,f);
err_ = sol2 - w;
err_abs = abs(err_);
err_max(i) = max(err_abs);
h1(i) = h;
end
table(h1', err_max')

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采纳的回答

Robert
Robert 2020-3-30
You can define the variables as columns before your for-loop:
h1 = zeros(16, 1);
err_max = zeros(16, 1);
By then assigning values to it, the variables remain columns.

更多回答（1 个）

Peng Li
Peng Li 2020-3-30
You can use h1(:) instead to make hi1 explicitely a column vector. This has a potential risk too if you h1 is actually a matrix as it will force it to reshape to a column vector.
For your code, what is your w like? no idea about your a, b, alpha, f variables.
Your outerloop is not necessary and can be optimized. Or at least, to improve efficiency, you'd better reallocate space for those variables that change size with loop.

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