Usage: 
{fh, clo, cup} = denxcb(x {,h {,alpha {,K} {,xv}}})

Input: 
 x  n x 1 vector, the data.

 h  scalar, bandwidth. If not given, the rule of
thumb bandwidth computed by denrot is used
(Silverman's rule of thumb).

 alpha  confidence level, If not given, 0.05 is used.

 K  string, kernel function on [1,1] with
K(1)=K(1)=0. If not given, the Quartic kernel
"qua" is used.

 xv  m x 1, values of the independent variable on
which to compute the density estimate. If not given,
x is used.

Output: 
 fh  n x 2 or m x 2 matrix, the first column is the
sorted first column of x or the sorted xv, the
second column contains the density estimate on
on the values of the first column. 
 clo  n x 2 or m x 2 matrix, the first column is the
sorted first column of x or the sorted xv, the
second column contains the lower confidence
bounds on the values of the first column. 
 cup  n x 2 or m x 2 matrix, the first column is the
sorted first column of x or the sorted xv, the
second column contains the upper confidence
bounds on the values of the first column. 