head() - shows first 10 rows
head(df)
tail() - shows last 10 rows
tail(df)
dim() - returns the dimensions of data frame (i.e. number of rows and number of columns)
dim(df)
nrow(df)
ncol(df)
colnames(df)
names(df)
colnames(df) <- c("col1", "col2", "col3")
rownames(df)
rownames(df) <- seq.int(nrow(df))
