30

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这种格式获得结果

  y    m Freq
 2010  1 2
 2010  2 2
 2010  3 1
 2011  1 1
 2011  2 1 
4

7 回答 7

39

如果您的数据是df带有列的数据框,y并且m

library(plyr)
counts <- ddply(df, .(df$y, df$m), nrow)
names(counts) <- c("y", "m", "Freq")
于 2012-06-04T10:40:28.637 回答
13

我还没有看到dplyr的答案。代码相当简单。

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))
于 2016-04-19T00:09:20.837 回答
8

@ugh 答案的更惯用的 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
于 2015-05-25T13:40:02.873 回答
5

使用sqldf

sqldf("SELECT y, m, COUNT(*) as Freq
       FROM table1
       GROUP BY y, m")
于 2012-06-04T10:11:51.643 回答
4

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很有用:

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
于 2012-06-04T14:23:47.110 回答
4

这是一个简单的基本R解决方案,使用table()andas.data.frame()

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))
于 2019-03-05T15:53:27.283 回答
3
library(data.table)

oldformat <- data.table(oldformat)  ## your orignal data frame
newformat <- oldformat[,list(Freq=length(m)), by=list(y,m)]
于 2013-01-04T23:12:11.557 回答