x=0:0.05:10; 
plot2d(x, x.*sin(x))
xbasc()                                    
subplot(221); plot2d(x, x.*sin(x),style=3)  
subplot(222); plot2d(x, x.*sin(x),style=-2) 
xset('line style', 2)
subplot(223); plot2d(x, x.*sin(x),style=5) 
xset('line style', 0)                     
subplot(224); plot2d(x', [x' (x.*sin(x))'], style=[3 5])
legends(['x'; 'x sin(x)'], [3 5])
xbasc()


nfois=1000;
Prems=1+floor(6*rand(1000,1));
Deuze=1+floor(6*rand(1000,1));
Jets=Prems+Deuze;
histplot(1:12, Jets) 


deff('y=surf(x,z)', 'y=z.*sqrt(1-x.^2)')
x=-1:0.05:1;
z=-5:0.1:5;
fplot3d(x,z,surf)

y=eval3d(surf, x,z); 
plot3d(x,z,y)


u=linspace(0,%pi, 50); 
v=linspace(-2, 2, 50);                                                           
deff('[x,y,z]=surf2(u,v)', ['x=cos(u).*ones(v)'; 'y=sin(u).*v'; 'z=ones(u).*v']) 
[x,y,z]=eval3dp(surf2, u,v);                                                    
plot3d(x,z,y)                                                                   



x=linspace(-5,5,50);   
y=linspace(-5,5,50);  
fcontour2d(x,y,f3)   

z=feval(x,y,f3);
contour2d(x,y,z,10)   

plot3d(x,y,z)                 
contour(x,y,z,10,flag=[0,1,0])


function x=collatz(n)  

x(1)=n; i=1;
while(x(i) ~= 1) 
if modulo(x(i), 2) then
  x(i+1)=3*x(i)+1
else
  x(i+1)=x(i)/2
end
i=i+1;
end
endfunction

exec('collatz.sci')
 
nfois=1000;
for i=1:nfois
lg(i)=length(collatz(i));
end
[k,i]=max(lg)

[find(lg>=100)' lg(lg>=100)]


for i=1:nfois         
gd(i)=max(collatz(i));
end
max(gd) 
sum(gd>10000)         




function x=bissect(a, b, f, tol)

fa = feval(a, f);
fb = feval(b, f);

while (abs(b-a)> tol) 
  mid=(a+b)/2;
  fmid=feval(mid, f);
  if (fa * fmid <=0) then
    b=mid; fb=fmid;
  else
    a=mid; fa=fmid;
  end  
end

x=(a+b)/2;
endfunction


deff('y=f4(x)', 'y=tan(x/4)-1')


x0=bissect(2,4,f4,1e-6)
format(20)
x0=bissect(2,4,f4,1e-15)