Problem with the plot of function besselj.

I have this code:

nu=1;
whitebg('k')
x=0:1e-3:9;
for n=1:4 
    paso=1/2^(n-1);
    y1=besselj(nu,x); 
    figure(n),close(n),figure(n) 
    hold on 
    plot(x,y1,'b')
    h=1e-5; 
    yder1=(besselj(nu,2+h)-besselj(nu,2))/h;
    yder2=(besselj(nu,8+h)-besselj(nu,8))/h; 
    nodos=2:paso:8; 
    yvalues=besselj(nu,nodos); 
    y2=spline(nodos,[0.009,yvalues,0.5588],x);
    plot(x,y2,'r')
    y3=spline(nodos,[yder1,yvalues,yder2],x);
    plot(x,y3,'w')
    y4=spline(nodos,yvalues,x);
    plot(x,y4,'g') 
    y5=interp1(nodos,yvalues,x); 
    plot(x,y5,'c')

      grid 
      title('Bessel function for nu=1')
      xlabel('Eje x') 
      ylabel('Eje y')
      legend('Besselj','Spline sujeto mal','Spline sujeto bien',...
          'Spline not-a-knot','Interp1','location','best')
  end

But I don't know why the graphs of the function 'besselj' seem to decrease with every iteration. I would like the function 'besselj' to always display the same plot, that's why the variable 'nu' is constant in my script.

Here's the link to function 'besselj':

http://www.mathworks.com/help/matlab/ref/besselj.html

Answer 1

[Roger Stafford]

As can be seen on the left side of your graphs, the scaling in the vertical “Eje y” axis is changing. The bessel curves are not really changing. It is the red spline that is getting worse each time. You should use a constant scaling factor in your plotting to see what is actually happening.

Answer 2

[Ricardo Boza Villar]

Thank you