MATLAB: How do i use imwrite

Image Processing Toolboximwrite

I have this code that plots a 3D Lorenz attractor. However when i try to write the plot to file using imwrite, it brings up an error:
Error in lorenzzz (line 31)
  imwrite(Lorenzattractor,'Lattractor','.png'); 
>>   
a=10; %sigma
b=8/3; %beta 
r=28; %rho
h=0.004; %time step size dt
x=0;y=1; z=0;
f=zeros(1,3); %creates an array to hold the values of x,y,z
f=[x y z]; 
k=1; %the first row of the array
for t=0:h:100 
    k1_x=a*(y(k)-x(k));
    k2_x=a*(y(k)-x(k))+(k1_x*h*0.5);
    k3_x=a*(y(k)-x(k))+(k2_x*h*0.5);
    k4_x=a*(y(k)-x(k))+(k3_x*h);
    x(k+1)=x(k)+(k1_x+2*k2_x+2*k3_x+k4_x)*h/6; %value of x at t+1
    k1_y=x(k)*(r-z(k))-y(k);
    k2_y=(x(k)*(r-z(k))-y(k))+k1_y*h*0.5;
    k3_y=(x(k)*(r-z(k))-y(k))+k2_y*h*0.5;
    k4_y=(x(k)*(r-z(k))-y(k))+k3_y*h*0.5;
    y(k+1)=y(k)+(k1_y+(2*k2_y)+(2*k3_y)+(k4_y))*h/6; %value of y at t+1
    k1_z=x(k)*y(k)-b*z(k);
    k2_z=(x(k)*y(k)-b*z(k))+k1_z*h*0.5;
    k3_z=(x(k)*y(k)-b*z(k))+k2_z*h*0.5;
    k4_z=(x(k)*y(k)-b*z(k))+k3_z*h*0.5;
    z(k+1)=z(k)+(k1_z+(2*k2_z)+(2*k3_z)+(k4_z))*h/6; %value of z at t+1 
    k=k+1;
end
    plot3(x,y,z); grid on;
    xlabel('x'); ylabel('y');
    zlabel('z'); 
    title('Lorenzattractor');
%the code runs up to this point.
    imwrite(Lorenzattractor,'Lattractor','.png');
brings error: Error in lorenzzz (line 31)
    imwrite(Lorenzattractor,'Lattractor','.png'); 
>>

Best Answer

Ejike I answered this earlier this morning. However somehow your question got deleted. Thanks to Lazarus, I still have my deleted answer. Here it is:
*Ejike: You do not have a variable in your program called Lorenzattractor. Anyway, you should be using export_fig. See the FAQ http://matlab.wikia.com/wiki/FAQ#How_do_I_save_my_figure.2C_axes.2C_or_image.3F_I.27m_having_trouble_with_the_built_in_MATLAB_functions.*
export_fig('Lattractor.png');
Also, please learn how to format your code. It's not hard, just make sure you have a blank line before it, then highlight all your code and click the {}Code icon above the edit box.
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