Select first 4 rows of a data.frame in R
Use head:
dnow <- data.frame(x=rnorm(100), y=runif(100))
head(dnow,4) ## default is 6
Using the index:
df[1:4,]
Where the values in the parentheses can be interpreted as either logical, numeric, or character (matching the respective names):
df[row.index, column.index]
Read help(`[`) for more detail on this subject, and also read about index matrices in the Introduction to R.