Zero-length Vector Issue in R

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The corner case of 0-length vectors is not well considered in R. It causes issues in several situations. First, 1:n is probably not what you want when n = 0. Second, df$col = 0 throws error when df is an empty (0 row) data frame. To avoid these issues, it is suggested that you write more robust R code.

# use 
seq_len(n)
# instead of 
1:n

# use 
for (i in seq_len(n)) {
    ...
}
# instead of 
for (i in 1:n) {
    ...
}

# use 
df$col = rep(x, nrow(df))
# instead of 
df$col = x             

Strings function in base R do not behavior well when zero-length vectors are involved. For example, paste('a', character(0)) returns a character vector of length 1 rather than length 0. Functions in the stringi packages works well when zero-length vectors are involved. For example, the code below returns a 0-length vector.

library(stringi)
'a' %s+% character(0)

It is suggested that you always use string functions in the stringi package rather than string functions in base R.