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')

[Stephen23]

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')

Answer 1

[David Hill]

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];

[LG]

Thank you!!

[Steven Lord]

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.

Answer 2

[Star Strider]

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')

.

[LG]

Thank you!!

[Star Strider]

My pleasure!