R中两列的频率计数

Question

我在数据框中有两列

2010  1
2010  1
2010  2
2010  2
2010  3
2011  1
2011  2

我想计算两列的频率并以此格式获得结果

  y    m Freq
 2010  1 2
 2010  2 2
 2010  3 1
 2011  1 1
 2011  2 1 

Answer 1

如果您的数据是包含df列和y

列的数据框m

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

Answer 2

我还没有看到 dplyr 的答案。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

数据：

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))

Answer 3

@ 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

Answer 4

使用sqldf：

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

Answer 5

如果你有一个包含很多列的非常大的数据框或者事先不知道列名，那么这样的东西可能会有用：

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

Answer 6

library(data.table)

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

Answer 7

这是使用R和table()的简单基础as.data.frame()解决方案

df2 <- as.data.frame(table(df1))
# df2 
     y m Freq
1 2010 1    2
2 2011 1    1
3 2010 2    2
4 2011 2    1
5 2010 3    1
6 2011 3    0

df2[df2$Freq != 0, ]
# output
     y m Freq
1 2010 1    2
2 2011 1    1
3 2010 2    2
4 2011 2    1
5 2010 3    1

数据

df1 <- 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))