dataframe - How to count and calculate percentages for two columns in an R data.frame? -

in r, have data.frame this:

df1 <- data.frame(   grade = rep(letters[1:5], 4),   sex = c(rep("male", 5), rep("female", 5), rep("male", 4), rep("female", 6)),   class = c(rep(1, 10), rep(2, 10)) )  df1     grade    sex class 1        male     1 2      b   male     1 3      c   male     1 4      d   male     1 5      e   male     1 6      female     1 7      b female     1 8      c female     1 9      d female     1 10     e female     1 11       male     2 12     b   male     2 13     c   male     2 14     d   male     2 15     e female     2 16     female     2 17     b female     2 18     c female     2 19     d female     2 20     e female     2 

i want count percentage of sex in each class , make data.frame like:

class male_percent female_percentage  1     50%          50%  2     40%          60% 

can teach me how it? question might have been asked before, don't know what's keyword question. sorry if ask same question again.

using data.table package can following

setdt(df)[ , .(                 male_percent = paste0(( nrow(.sd[sex == "male"]) / .n ) * 100 , "%")   ,                  female_percent = paste0(( nrow(.sd[sex == "female"]) / .n ) * 100 , "%")               )   ,             = class          ] 

result

#     class      male_percent  female_percent # 1:     1          50%            50% # 2:     2          40%            60% 

another dplyr solution

df %>%   group_by(sex , class) %>%   summarise(n = n()) %>%   group_by(class) %>%   summarise(     male_percent = paste0((n[sex == "male"] / sum(n)) * 100 , "%")    ,      female_percent = paste0((n[sex == "female"] / sum(n) * 100) , "%")      )  #  class   male_percent     female_percent #   1          50%            50% #   2          40%            60%