maybe you are looking for melt.data.table(data, id.vars = c('data','firm'))
Den 10/04/17 kl. 15:44, skrev Lask_Linz:
long format
_______________________________________________ datatable-help mailing list datatable-help@lists.r-forge.r-project.org https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help