tvIRF returns and object of class tvirf with the 
following components:
irfA list of length the number of impulse variable(s). Each element
of the list is an array of dim = c(obs x number 
of response variables x n.ahead).
LowerA list of length the number of impulse variable(s), containing
 the lower confidence line, if calculated.
UpperA list of length the number of impulse variable(s), containing
 the upper confidence line, if calculated.
responseA character, a number of a vector with the names or 
positions of the response(s) variable(s).
impulseA character, a number of a vector with the names or 
positions of the impulse(s) variable(s).
xA object of class tvvar
.
n.aheadNumber of ahead impulse response functions.
orthoLogical, orthogonal or not impuluse response function.
ortho.covCharacter, either 'const' or 'tv' (default). This 
parameter is used when the orthogonal TVIRF is calculated. The default 
is using an error time-varying variance-covariance.
bw.covA scalar with the bandwidth to estimate the errors 
variance-covariance matrix. If NULL, it is calculated by cross-validation.
cumulativeLogical, if TRUE the cumulated impulse response 
coefficients are computed. Default is FALSE.