# Create a pdata.frame and extract a series, which becomes a pseries
data("EmplUK", package = "plm")
Em <- pdata.frame(EmplUK)
z <- Em$output
class(z) # pseries as indicated by class
is.pseries(z) # and confirmed by check
# destroy index of pseries and re-check
attr(z, "index") <- NA
is.pseries(z) # now FALSE
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