Talvez algo assim...
### <code r>
{
set.seed(123)
df <- data.frame(
municipio=sample(c("Limeira", "Manaus", "Dourados"), 30, repl=T),
diasemanaincident=sample(c("terca", "quarta", "sexta"), 30, repl=T),
trechoklmetros=sample(0:400000, 30),
turnoincidente=sample(c("manha", "tarde"), 30, repl=T), stringsAsFactors=F)
}
which(df$municipio == 'Limeira')
# [1] 1 6 15 17 18 19 29 30
which(df$municipio == 'Limeira' & df$diasemanaincident == 'terca')
# [1] 15 17 19
vec <- c("df$municipio == 'Limeira'",
"df$municipio == 'Limeira' & df$diasemanaincident == 'terca'"); cbind(vec)
for (a in vec) print(with(df, which(eval(parse(text=a)))))
# [1] 1 6 15 17 18 19 29 30
# [1] 15 17 19
### </code>