require help

hello to all. I am working on macroeconomic data series of India, which in
a yearly basis. I am unable to convert my data frame into time series.
kindly help me.
also using zoo and xts packages. but they take only monthly observations.

'data.frame': 30 obs. of  4 variables:
 $ year: int  1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 ...
 $ cnsm: num  174 175 175 172 173 ...
 $ incm: num  53.4 53.7 53.5 53.2 53.3 ...
 $ wlth: num  60.3 60.5 60.2 60.1 60.7 ...

Yadawananda Neog
Research Scholar
Department of Economics
Banaras Hindu University
Mob. 9838545073

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