Вам не нужен второй стол,
library(dplyr)
df <- data.frame(Country = rep(c("Alemania", "España", "Francia"), each = 2), Gender = rep(c("Mujer", "Hombre"), 3), freq = c(899, 5266, 1569, 5582, 1398, 5054))
df %>% group_by(Country) %>% mutate(total = sum(freq)) %>% mutate(percentage = 100*freq/total) %>% select(Country, Gender, percentage)
, который выглядит как:
1 Alemania Mujer 14.6
2 Alemania Hombre 85.4
3 España Mujer 21.9
4 España Hombre 78.1
5 Francia Mujer 21.7
6 Francia Hombre 78.3