The graph is coming out blank

1 次查看（过去 30 天）
LG
LG 2022-5-30
编辑： DGM 2022-6-20
The graph for plot(x0,y0) comes out with no values, it´s blank. How can I solve this?
clear all
clc
f=@(x,y) -y/.1; %función a resolver
x0=input('\n Ingrese el valor inicial de x0: '); % x inicial
y0=input('\n Ingrese el valor inicial de y0: '); % y inicial
xn=input('\n Ingrese el valor final de x: ');% hasta donde llega x
h=input('\n Ingrese el valor de paso h: '); %intervalo
fprintf('\n x y ');
while x0<=xn
hold on
plot(x0,y0)
fprintf('\n%4.3f %4.6f ',x0,y0); %valores de "x" y "y"
k1= f(x0,y0);
k2= f(x0+.5*h,y0+.5*h*k1);
k3= f(x0+.5*h,y0+.5*k2*h);
k4= f(x0+h,y0+k3*h);
x1=x0+h;
y1=y0+1/6*(k1+2*k2+2*k3+k4)*h;
x0=x1;
y0=y1;
end
fprintf('\n');
xspan=[0 1]
[x,y] = ode45(@(x,y) -y/.1,xspan,2); %comprobar o comparar con la función que nos da Matlab
plot(x,y)
title('funcion matlab')
  1 个评论
Stephen23
Stephen23 2022-6-16
编辑：Stephen23 2022-6-16
Original question by Lizeth Armida García Valle retrieved from Google Cache:
https://web.archive.org/web/20220616123945/https://webcache.googleusercontent.com/search?q=cache%3A9DyWi44crS8J%3Ahttps%3A%2F%2Fwww.mathworks.com%2Fmatlabcentral%2Fanswers%2F1729680-the-graph-is-coming-out-blank
https://web.archive.org/web/20220616124310/https://www.mathworks.com/matlabcentral/answers/1729680-the-graph-is-coming-out-blank
The graph for plot(x0,y0) comes out with no values, it´s blank. How can I solve this?
clear all
clc
f=@(x,y) -y/.1; %función a resolver
x0=input('\n Ingrese el valor inicial de x0: '); % x inicial
y0=input('\n Ingrese el valor inicial de y0: '); % y inicial
xn=input('\n Ingrese el valor final de x: ');% hasta donde llega x
h=input('\n Ingrese el valor de paso h: '); %intervalo
fprintf('\n x y ');
while x0<=xn
hold on
plot(x0,y0)
fprintf('\n%4.3f %4.6f ',x0,y0); %valores de "x" y "y"
k1= f(x0,y0);
k2= f(x0+.5*h,y0+.5*h*k1);
k3= f(x0+.5*h,y0+.5*k2*h);
k4= f(x0+h,y0+k3*h);
x1=x0+h;
y1=y0+1/6*(k1+2*k2+2*k3+k4)*h;
x0=x1;
y0=y1;
end
fprintf('\n');
xspan=[0 1]
[x,y] = ode45(@(x,y) -y/.1,xspan,2); %comprobar o comparar con la función que nos da Matlab
plot(x,y)
title('funcion matlab')

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回答（2 个）

David Hill
David Hill 2022-5-30
Index and plot after completion of loop.
f=@(x,y) -y/.1;
x=input('\n Ingrese el valor inicial de x0: ');
y=input('\n Ingrese el valor inicial de y0: ');
xn=input('\n Ingrese el valor final de x: ');
h=input('\n Ingrese el valor de paso h: ');
while x(end)<=xn
k1= f(x(end),y(end));
k2= f(x(end)+.5*h,y(end)+.5*h*k1);
k3= f(x(end)+.5*h,y(end)+.5*k2*h);
k4= f(x(end)+h,y(end)+k3*h);
x(end+1)=x(end)+h;
y(end+1)=y(end)+1/6*(k1+2*k2+2*k3+k4)*h;
end
plot(x,y);
xspan=[0 1];
  2 个评论
Steven Lord
Steven Lord 2022-5-30
Alternately you could create an animatedline prior to entering the loop and call addpoints on its handle inside the loop to add points to the animated line.

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Star Strider
Star Strider 2022-5-30
Ran in:
Try this —
f=@(x,y) -y/.1; %función a resolver
% x0=input('\n Ingrese el valor inicial de x0: '); % x inicial
% y0=input('\n Ingrese el valor inicial de y0: '); % y inicial
% xn=input('\n Ingrese el valor final de x: ');% hasta donde llega x
%
% h=input('\n Ingrese el valor de paso h: '); %intervalo
x0 = 0;
y0 = 2;
xn = 1;
h = 1E-1;
fprintf('\n x y ');
x y
figure
while x0<=xn
hold on
plot(x0,y0,'pg', 'MarkerSize',7)
fprintf('\n%4.3f %4.6f ',x0,y0); %valores de "x" y "y"
k1= f(x0,y0);
k2= f(x0+.5*h,y0+.5*h*k1);
k3= f(x0+.5*h,y0+.5*k2*h);
k4= f(x0+h,y0+k3*h);
x1=x0+h;
y1=y0+1/6*(k1+2*k2+2*k3+k4)*h;
x0=x1;
y0=y1;
end
0.000 2.000000 0.100 0.750000 0.200 0.281250 0.300 0.105469 0.400 0.039551 0.500 0.014832 0.600 0.005562 0.700 0.002086 0.800 0.000782 0.900 0.000293 1.000 0.000110
fprintf('\n');
xspan=[0 1];
[x,y] = ode45(@(x,y) -y/.1,xspan,2); %comprobar o comparar con la función que nos da Matlab
hold on
plot(x,y,'-k')
hold off
title('funcion matlab')
.

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