[R] problem with urca package

[hassen62 at voila.fr]

Dear R users,
I have the joined txt file in the following direct directory C://
I have written the following lines:
library(urca);
PIBTUN<-read.table("C:/AF.txt", header=F);
ur.df(PIBTUN,type='none',lags=1)
but I have obtained the following message:
Error in embed(z, lags) : 'x' is not a vector or matrix
I don't What's the problem, can you please help me
Thank you in advance

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