如何计算满足R中特定条件的观测值

Question

我有以下数据框：

  df <- structure(list( data = structure(1:10, .Label = c("Ind_1", "Ind_2", "Ind_3" , "Ind_4" , "Ind_5" , "Ind_6" 
, "Ind_7" , "Ind_8" , "Ind_9" , "Ind_10" ), class = "factor"),
    hoursworked_week = c(4,9,12,45,23,18,23,45,16,7), job_status = c(4,2,1,7,4,5,3,2,4,4)),
                class = "data.frame", row.names=c(NA,-10L))

     data hoursworked_week job_status
1   Ind_1                4          4
2   Ind_2                9          2
3   Ind_3               12          1
4   Ind_4               45          7
5   Ind_5               23          4
6   Ind_6               18          5
7   Ind_7               23          3
8   Ind_8               45          2
9   Ind_9               16          4
10 Ind_10                7          4

我想计算有hoursworked_week <= 20 & job_status == 4

个

我尝试过 count(df$hoursworked_week <= 20 & df$job_status == 4，但无效