我的数据框由个人和他们在某个时间点居住的城市组成。我想为每年生成一个起点-终点矩阵,记录从一个城市到另一个城市的移动次数。我想知道:
考虑以下示例:
#An example dataframe
id=sample(1:5,50,T)
year=sample(2005:2010,50,T)
city=sample(paste(rep("City",5),1:5,sep=""),50,T)
df=as.data.frame(cbind(id,year,city),stringsAsFactors=F)
df$year=as.numeric(df$year)
df=df[order(df$id,df$year),]
rm(id,year,city)
我最好的尝试
#Creating variables
for(i in 1:length(df$id)){
df$origin[i]=df$city[i]
df$destination[i]=df$city[i+1]
df$move[i]=ifelse(df$orig[i]!=df$dest[i] & df$id[i]==df$id[i+1],1,0) #Checking whether a move has taken place and whether its the same person
df$year_move[i]=ceiling((df$year[i]+df$year[i+1])/2) #I consider that the person has moved exactly between the two dates at which its location was recorded
}
df=df[df$move!=0,c("origin","destination","year_move")]
创建 2007 年的起点-终点表
yr07=df[df$year_move==2007,]
table(yr07$origin,yr07$destination)
结果
City1 City2 City3 City5
City1 0 0 1 2
City2 2 0 0 0
City5 1 1 0 0
最佳答案
您可以按 id 拆分数据,对特定于 id 的数据框执行必要的计算以获取该人的所有 Action ,然后重新组合:
spl <- split(df, df$id)
move.spl <- lapply(spl, function(x) {
ret <- data.frame(from=head(x$city, -1), to=tail(x$city, -1),
year=ceiling((head(x$year, -1)+tail(x$year, -1))/2),
stringsAsFactors=FALSE)
ret[ret$from != ret$to,]
})
(moves <- do.call(rbind, move.spl))
# from to year
# 1.1 City4 City2 2007
# 1.2 City2 City1 2008
# 1.3 City1 City5 2009
# 1.4 City5 City4 2009
# 1.5 City4 City2 2009
# ...
因为此代码对每个 id 使用矢量化计算,所以它应该比在提供的代码中循环遍历数据帧的每一行要快得多。
现在您可以使用
split
获取特定年份的 5x5 移动矩阵和 table
:moves$from <- factor(moves$from)
moves$to <- factor(moves$to)
lapply(split(moves, moves$year), function(x) table(x$from, x$to))
# $`2005`
#
# City1 City2 City3 City4 City5
# City1 0 0 0 0 1
# City2 0 0 0 0 0
# City3 0 0 0 0 0
# City4 0 0 0 0 0
# City5 0 0 1 0 0
#
# $`2006`
#
# City1 City2 City3 City4 City5
# City1 0 0 0 1 0
# City2 0 0 0 0 0
# City3 1 0 0 1 0
# City4 0 0 0 0 0
# City5 2 0 0 0 0
# ...
关于r - 使用 R 创建起点-终点矩阵,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/30263023/