How to fill a vector and change its elements when reaching a specific element?

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Maria
Maria 2022-11-17
评论： Maria 2022-11-17
Hi all!
i want to fill a row vector X=1*3600 as x(j+1)=x(j)+20, and elements of X should be 0<=x<=1000.
for example :
x(1)=0
x(2)=20
x(3)=40,
.....
and when arriving x(j)=1000, x(j+1)=x(j)-20 as following :
x(j)=1000
x(j+1)=980
x(j+2)=960,
......
and when coming to "0" , it will start again x(j+1)=x(j)+20. i want to repeat that until arriving at the column 3600.
thanks in advance

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采纳的回答

Bruno Luong
Bruno Luong 2022-11-17
Ran in:
x = zeros(1, 3600);
x(1) = 0;
dx = 20;
for k=2:length(x)
xk = x(k-1) + dx;
if xk > 1000
dx = -20;
xk = x(k-1) + dx;
elseif xk < 0
dx = 20;
xk = x(k-1) + dx;
end
x(k) = xk;
end
plot(x,'o-')
  3 个评论
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Bruno Luong
Bruno Luong 2022-11-17
A variant, avoid repeating code
x = zeros(1, 3600);
x(1) = 0;
dx = 20;
k = 1;
while k < length(x)
xk = x(k) + dx;
if xk > 1000
dx = -20;
elseif xk < 0
dx = 20;
else
k = k+1;
x(k) = xk;
end
end

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更多回答（1 个）

Image Analyst
Image Analyst 2022-11-17
Ran in:
Try this:
maxx = 1000;
x = zeros(1, 3600);
index = 2;
while x(index-1) < maxx && index < length(x)
x(index) = x(index-1) + 20;
index = index + 1;
end
for k = index : length(x)
x(k) = x(k-1) - 20;
% Quit if x goes negative
if x(k) < 0
break;
end
end
% Show in command window
x
x = 1×3600
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560 580
  4 个评论
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Maria
Maria 2022-11-17
编辑：Maria 2022-11-17
@Image Analyst it is not a homework, just i'm asking for a simple way to don't repeat the while loop for many times. i posted my question not because i don't know how to write a code with loop but to find an easier manner .
i wrote that elements of x are between 0 and 1000 , i think that you understand that i want to fill all elements of x.
Image Analyst
Image Analyst 2022-11-17
OK, looks like you're going to use Bruno's answer so I won't bother. You can increase your skills by investing 2 hours here:
MATLAB Academy - Free 2 hour training

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