gap in the plot

2019 10 31
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更新时间：2019 10 31
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Снимок.PNG
How can I make the red plot start in the same place (from 1)?

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回答（1 个）

Walter Roberson
Walter Roberson 2019-10-31

0 个投票

red_x = red_x - min(red_x) + 1;
plot(blue_x, blue_y, 'b', red_x, red_y, 'r')

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Valeria Pinus
Valeria Pinus 2019-10-31
This has just created a gap on the other side and moved the whole plot :(
Снимок.PNG
Walter Roberson
Walter Roberson 2019-10-31
Yes, that is to be expected. You did not specify that was not to happen.
It looks to me as if whatever process generated the data for the red line did not start from the same position. However, you have not given us any information about how the red line was generated, so we can only make wild guesses.
Valeria Pinus
Valeria Pinus 2019-10-31
My bad. Here is the code:
X=[1 2 3 4 5 6 7 8 9]; %госдолг сша
Y=[120.7 26.0 162.0 50.7 256.9 290.5 380.9 90.9 20.6];
xzv=5.5;
xi=min(X):0.05:max(X); % Вспомогательный вектор абсциссы
yi=spline(X,Y,xi);
plot(X,Y,'*k',xi,yi,'b');grid;hold on; % Построение графика
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
s3x=form2(X,Y,S,xzv) %значение s3(x*)
dx=(max(X)-min(X))/50; % Вычисление шага
for i=(1:50)
xi_new(i)=min(X)+dx*i; % Вспомогательные точки абсциссы
zi(i)=form2(X,Y,S,xi_new(i)); % Значение S3 в точке xi(i)
end
plot(X,Y,'*k',xi_new,zi,'r');hold off; % Построение графика
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);
Walter Roberson
Walter Roberson 2019-10-31
Perhaps
xi_new(i)=min(X)+dx*i;
should be
xi_new(i)=min(X)+dx*(i-1);
?
Valeria Pinus
Valeria Pinus 2019-10-31
that way it says
Unable to perform assignment because the left and right sides have a different number of elements.
Error in lesson5_1 (line 24)
zi(i)=form2(X,Y,S,xi_new(i));
Walter Roberson
Walter Roberson 2019-10-31
I see.
Your processing requires a gap. In form2 you have
i=max(find(X<z));
which would be empty if z is exatly equal to the first X because you are attempting to process right to the left margin.
You can reduce the width of the gap by reducing dx, but you cannot eliminate the gap.

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