Error using plot Vectors must be the same length.

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Valeria Pinus
Valeria Pinus 2019-10-28
编辑： KALYAN ACHARJYA 2019-10-28
So I've got an error in plot:
Error using plot
Vectors must be the same length.
Error in lesson5_1 (line 25)
plot(X,Y,'*k',xi,zi);grid
% Построение графика
Here is the code;
X=[1910 1920 1930 1940 1950 1960 1970 1980 1990]-1909; %госдолг сша
Y=[120.7 26.0 162.0 50.7 256.9 290.5 380.9 90.9 20.6];
xzv=1955-1909;
xi=min(X):0.05:max(X); % Вспомогательный вектор абсциссы
yi=spline(X,Y,xi);
AS=[2 1 0 0 0 0 0 0 0;
1 4 1 0 0 0 0 0 0;
0 1 4 1 0 0 0 0 0;
0 0 1 4 1 0 0 0 0;
0 0 0 1 4 1 0 0 0;
0 0 0 0 1 4 1 0 0;
0 0 0 0 0 1 4 1 0;
0 0 0 0 0 0 1 4 1;
0 0 0 0 0 0 0 1 2];
BS=3.*[26.0-120.7;162.0-120.7;50.7-26.0;
256.9-162.0;290.5-50.7;380.9-256.9;
90.9-290.5;20.6-380.9;20.6-90.9];
S=AS\BS;
dx=(max(X)-min(X))/50; % Вычисление шага
for i=(1:50),
xi(i)=min(X)+dx*i; % Вспомогательные точки абсциссы
zi(i)=form2(X,Y,S,xi(i)); % Значение S3 в точке xi(i)
end;
plot(X,Y,'*k',xi,zi);grid % Построение графика
And here is the function form2:
function y=form2(X,Y,S,z);
i=max(find(X<z));
h=X(i+1)-X(i);
p=(X(i+1)-z)/h;
q=(z-X(i))/h;
y=p^2*(2*q+1)*Y(i)+p^2*q*S(i)+...
q^2*(2*p+1)*Y(i+1)-q^2*p*S(i+1);
What could be the problem?

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采纳的回答

KALYAN ACHARJYA
KALYAN ACHARJYA 2019-10-28
No Error
678.png
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KALYAN ACHARJYA
KALYAN ACHARJYA 2019-10-28
编辑：KALYAN ACHARJYA 2019-10-28
The reason, the later xi just replaced the previous 50 elements of the initial xi vector and maintained the same length.
Lets example you defined xi as following
xi=0:1:10 % Length eleven
for i=1:5
xi(i)=i*3;
y(i)=..
end
In the second loop, it replace the initial 5 elements of the xi, but it maintained the initial length of xi, and y reflects the length of equal to the loop iteration. So you cant plot xi and yi
Always assign the new variable name to avoid such clashing the variables name, if memory allows.
Hope it helps

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