On 2012-04-20 12:10, danipaty13 wrote: > Thanks for your answer well, I uploaded a file with my data, hope you can > help me to solve my problem since i'm using R for my thesis > http://r.789695.n4.nabble.com/file/n4574997/invgrosor.csv invgrosor.csv Are you sure that's the data you're posting about? Peter Ehlers