>> A= randi(9, 4, 4)

A =

     8     6     9     9
     9     1     9     5
     2     3     2     8
     9     5     9     2

>> chol(A)
Error using chol
Matrix must be positive definite.
 
>> B= A+ diag(27*ones(4,1))

B =

    35     6     9     9
     9    28     9     5
     2     3    29     8
     9     5     9    29

>> R=chol(B);
>> R

R =

    5.9161    1.0142    1.5213    1.5213
         0    5.1934    1.4359    0.6657
         0         0    4.9623    0.9532
         0         0         0    5.0333

>> R'*R

ans =

   35.0000    6.0000    9.0000    9.0000
    6.0000   28.0000    9.0000    5.0000
    9.0000    9.0000   29.0000    8.0000
    9.0000    5.0000    8.0000   29.0000

>> R=chol(B, 'lower')

R =

    5.9161         0         0         0
    1.5213    5.0681         0         0
    0.3381    0.4905    5.3521         0
    1.5213    0.5299    1.5369    4.9033