tsdiag error

Does anyone know why I get the following error when trying tsdiag?

    Error in UseMethod("tsdiag") : no applicable method for "tsdiag"

I am invoking it as: tsdiag(mar).

tsdiag is a generic function that tries to dispatch for "mar", but there 
is no appropriate method available that is able to deal with objects of 
class of "mar". Hence check what classes of objects you can specify for 
tsdiag() and of which class "mar" currently is.

Uwe Ligges

Thank you.

Kevin

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