在 R 中过滤来自 table 的记录

Question

我有一个数据集电影。

head(Movies)

如何获取 MovieID 为“0000008”的行？我试过：

t1 = subset(Movies, "MovieID" == "0000008")
t2 <- Movies[ which(Movies["MovieID"]=="0000008"), ]
head(t1)
head(t2)

两个 return 空数据集，这是错误的，因为我可以看到 ID 为“0000008”的行。

编辑：我尝试从 MovieID 中删除“”，但会引发错误：

Error in subset.matrix(Movies, MovieID == "0000008"): object 'MovieID' not found

编辑：电影数据获得为：

URL = "https://raw.githubusercontent.com/sidooms/MovieTweetings/master/latest/movies.dat"
MovieText = readLines( remote.file(URL) ) # HACK!!!
Movies = matrix( sapply( MovieText,
            function(x) unlist(strsplit(sub(" [(]([0-9]+)[)]", "::\1",x),"::"))[1:4] ),
            nrow=length(MovieText), ncol=4, byrow=TRUE )
colnames(Movies) = c("MovieID", "MovieTitle", "Year", "Genres")

Answer 1

你的nrow应该是length(MovieText)/4

URL = "https://raw.githubusercontent.com/sidooms/MovieTweetings/master/latest/movies.dat"
MovieText = readLines( URL ) # HACK!!!
Movies = matrix( sapply( MovieText,
    function(x) unlist(strsplit(sub(" [(]([0-9]+)[)]", "::\1",x),"::"))[1:4] ),
    nrow=length(MovieText)/4, ncol=4, byrow=TRUE )
colnames(Movies) = c("MovieID", "MovieTitle", "Year", "Genres")

#if you want to work with matrix, then use this
subset(Movies, Movies[,"MovieID"]=="0000008")

编辑：`data.frame` 和 `data.table` 子集

library(data.table)

MoviesDF <- data.frame(Movies)
MoviesDT <- data.table(Movies)

MoviesDF[MoviesDF["MovieID"] == "0000008", ]
MoviesDT[MovieID == "0000008", ]

顺便说一句：喜欢 HACK!!! 评论。

在 R 中过滤来自 table 的记录

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jupyter-irkernel

编辑：`data.frame` 和 `data.table` 子集

在 R 中过滤来自 table 的记录

Filter records from table in R

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jupyter-irkernel

编辑：data.frame 和 data.table 子集

编辑：`data.frame` 和 `data.table` 子集