Alternative for linspace?

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Sarah Gomez
Sarah Gomez 2022-2-11
评论： VBBV 2024-2-25
function [xvals, yvals]=A5fourier(L,nmax,numpoints)
%xvals=linspace(-L,L,numpoints);
for z=-0.1:0.001:0.1
xvals=z;
end
yvals=zeros(1,numpoints);
for i=1:numpoints
for j=1:2:nmax
yvals(i)=(4/pi)*(yvals(i)+(1/j)*sin(j*pi*xvals(i)/L));
j=j+1;
end
i=i+1;
end
L in this function is 0.1, and numpoints is 200. I've been challenged to use a loop rather than linspace to create the same 200 equally spaced points. My current solution ruins my yvals part of the function returning an error "Index exceeds the number of array elements". How can I remedy linspace while mainting the rest of my function?

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回答（1 个）

DGM
DGM 2022-2-11
编辑：DGM 2022-2-11
Ran in:
Why not just use the colon operator?
r = [-4 4];
n = 10;
x1 = linspace(r(1),r(2),n)
x1 = 1×10
-4.0000 -3.1111 -2.2222 -1.3333 -0.4444 0.4444 1.3333 2.2222 3.1111 4.0000
x2 = r(1):range(r)/(n-1):r(2)
x2 = 1×10
-4.0000 -3.1111 -2.2222 -1.3333 -0.4444 0.4444 1.3333 2.2222 3.1111 4.0000
This can definitely be simplified. The iterator in a for-loop doesn't need to be incremented.
yvals=zeros(1,numpoints);
for i=1:numpoints
for j=1:2:nmax
yvals(i)=(4/pi)*(yvals(i)+(1/j)*sin(j*pi*xvals(i)/L));
% j=j+1; % this doesn't do anything
end
% i=i+1; % this doesn't do anything
end
  1 个评论
VBBV
VBBV 2024-2-25
Ran in:
@Sarah Gomez, if your question involves, to use the for loops /other loops to create linearly spaced points, then this could be one option to do so, however, there are several redundant lines of code in your function whcih @DGM pointed out. Further, ihe simplest altrenative would be to use the colon : operator which also was mentioned by @DGM
[xvals yvals] = A5fourier(0.1,200,200)
xvals = 1×201
-0.1000 -0.0990 -0.0980 -0.0970 -0.0960 -0.0950 -0.0940 -0.0930 -0.0920 -0.0910 -0.0900 -0.0890 -0.0880 -0.0870 -0.0860 -0.0850 -0.0840 -0.0830 -0.0820 -0.0810 -0.0800 -0.0790 -0.0780 -0.0770 -0.0760 -0.0750 -0.0740 -0.0730 -0.0720 -0.0710
yvals = 1×200
1.0e+10 * -0.0000 -0.4436 -0.8361 -1.1547 -1.4027 -1.5940 -1.7426 -1.8596 -1.9533 -2.0295 -2.0925 -2.1452 -2.1898 -2.2280 -2.2609 -2.2896 -2.3148 -2.3370 -2.3567 -2.3743 -2.3901 -2.4043 -2.4171 -2.4286 -2.4392 -2.4487 -2.4575 -2.4654 -2.4727 -2.4794
linspace(-0.1,0.1,200)
ans = 1×200
-0.1000 -0.0990 -0.0980 -0.0970 -0.0960 -0.0950 -0.0940 -0.0930 -0.0920 -0.0910 -0.0899 -0.0889 -0.0879 -0.0869 -0.0859 -0.0849 -0.0839 -0.0829 -0.0819 -0.0809 -0.0799 -0.0789 -0.0779 -0.0769 -0.0759 -0.0749 -0.0739 -0.0729 -0.0719 -0.0709
function [xvals, yvals]=A5fourier(L,nmax,numpoints)
%xvals=linspace(-L,L,numpoints);
% alternative to linspace using for loops !!!
k = 1;
for z=-0.1:0.001:0.1
xvals(k)=z;
k = k+1;
end
yvals=zeros(1,numpoints);
for i=1:numpoints
for j=1:2:nmax
yvals(i)=(4/pi)*(yvals(i)+(1/j)*sin(j*pi*xvals(i)/L));
end
end
end

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