R中两列的频率计数

6 回答

• 4

  @ ugh的答案更为惯用的data.table版本是：

  library(data.table) # load package
  df <- data.frame(y = c(rep(2010, 5), rep(2011,2)), m = c(1,1,2,2,3,1,2)) # setup data
  dt <- data.table(df) # transpose to data.table
  dt[, list(Freq =.N), by=list(y,m)] # use list to name var directly
  

  回复于 2024-05-01T09:22:36+08:00
• 27

  如果您有一个包含许多列的非常大的数据框或者事先不知道列名，那么这样的事情可能会有用：

  library(reshape2)
  df_counts <- melt(table(df))
  names(df_counts) <- names(df)
  colnames(df_counts)[ncol(df_counts)] <- "count"
  df_counts    
  
    y    m     count
  1 2010 1     2
  2 2011 1     1
  3 2010 2     2
  4 2011 2     1
  5 2010 3     1
  6 2011 3     0
  

  回复于 2024-05-01T09:22:36+08:00
• 3

  我还没有看到dplyr的回答 . 代码很简单 .

  library(dplyr)
  rename(count(df, y, m), Freq = n)
  # Source: local data frame [5 x 3]
  # Groups: V1 [?]
  #
  #       y     m  Freq
  #   (int) (int) (int)
  # 1  2010     1     2
  # 2  2010     2     2
  # 3  2010     3     1
  # 4  2011     1     1
  # 5  2011     2     1
  

  Data:

  df <- structure(list(y = c(2010L, 2010L, 2010L, 2010L, 2010L, 2011L, 
  2011L), m = c(1L, 1L, 2L, 2L, 3L, 1L, 2L)), .Names = c("y", "m"
  ), class = "data.frame", row.names = c(NA, -7L))
  

  回复于 2024-05-01T09:22:36+08:00
• 7

  library(data.table)
  
  oldformat <- data.table(oldformat)  ## your orignal data frame
  newformat <- oldformat[,list(Freq=length(m)), by=list(y,m)]
  

  回复于 2024-05-01T09:22:36+08:00
• 10

  使用 sqldf ：

  sqldf("SELECT y, m, COUNT(*) as Freq
         FROM table1
         GROUP BY y, m")
  

  回复于 2024-05-01T09:22:36+08:00
• 4

  如果您的数据是数据框 df ，其列为 y 和 m

  library(plyr)
  counts <- ddply(df, .(df$y, df$m), nrow)
  names(counts) <- c("y", "m", "Freq")
  

  回复于 2024-05-01T09:22:36+08:00