-------- regression diagnostic functions -------- 

 
arch            : computes a test for ARCH(p)    
arch_d          : demo of arch() test for ARCH(p)
bkw             : computes and prints BKW collinearity diagnostics
bkw_d           : demo of bkw() 
bpagan          : Breusch-Pagan heteroscedasticity test
bpagan_d        : An example of  bpagan(),
cusums          : computes cusum-squares test 
cusums_d        : demo of rec_resid()
dfbeta          : computes BKW (influential observation diagnostics)
dfbeta_d        : demo of dfbeta(), plt_dfb()
rdiagnose        : computes regression diagnostic measures (see RETURNS)
rdiagnose_d      : demo of diagnose()
plt_cus         : plots cusum squared tests
plt_dfb         : plots BKW influential observation diagnostics
plt_dff         : plots BKW influential observation diagnostics
qstat2          : computes the Ljung-Box Q test for AR(p)   
qstat2_d        : demo of qstat2() Ljunbg-Box Q test
rdiag           : residual analysis plots
rdiag_d         : demo of rdiagn()
recresid        : compute recursive residuals
recresid_d      : demo of recresid()
studentize      : If x is a vector, subtract its mean and divide
unstudentize    : returns reverse studentized vector 
unstudentize_d  : demonstrate unstudentize function