R 基于字符串条件创建子集

拥有这样的数据帧：

df_in <- data.frame(x = c('x1','x2','x3','x4'),
                     col1 = c('http://youtube.com/something','NA','https://www.yahooexample.com','https://www.yahooexample2.com'),
                     col2 = c('https://google.com', 'http://www.bbcnews2.com?id=321','NA','https://google.com/text'),
                     col3 = c('http://www.bbcnews.com?id=321', 'http://google.com?id=1234','NA','https://bbcnews.com/search'),
                     col4 = c('NA', 'https://www.youtube/com','NA', 'www.youtube.com/searcht'))

我想创建一个特定子集条件的数据帧。例如，我只想保留一个包含“谷歌”、“youtube”和“bbc”的标签。 预期产出示例：

df_out <- data.frame(x = c('x1','x2','x4'),
                     col1new = c('http://youtube.com/something', 'http://www.bbcnews2.com?id=321', 'https://google.com/text'),
                     col2new = c('https://google.com', 'http://google.com?id=1234', 'https://bbcnews.com/search'),
                     col3new = c('http://www.bbcnews.com?id=321', 'https://www.youtube/com', 'www.youtube.com/searcht'))

---

我们可以使用

grep

创建逻辑条件，根据

http://

i1 <- Reduce('|', lapply(df_in[-1], grepl, pattern= "https?://(google|youtube|bbc)"))

和

cbind

以及第一列的子集

cbind(df_in[i1, 1, drop = FALSE], tmp)
#   x                        col1new                    col2new                       col3new
#1 x1   http://youtube.com/something         https://google.com http://www.bbcnews.com?id=321
#2 x2 http://www.bbcnews2.com?id=321  http://google.com?id=1234       https://www.youtube/com
#4 x4        https://google.com/text https://bbcnews.com/search       www.youtube.com/searcht

---

你试过什么？当你的搜索小组发现你的情况时会发生什么？例如

bbc

中的

youtube

<代码>https://www.youtube.com/results?search_query=bbc您可能需要

i1的输出是什么：
df\u in
i1 <- Reduce('|', lapply(df_in[-1], grepl, pattern= "https?://(google|youtube|bbc)"))

tmp <- t(apply(df_in[i1,-1], 1, function(x) x[grepl("(google|youtube|bbc)", x)]))
colnames(tmp) <- paste0('col', seq_len(ncol(tmp)), "new")

cbind(df_in[i1, 1, drop = FALSE], tmp)
#   x                        col1new                    col2new                       col3new
#1 x1   http://youtube.com/something         https://google.com http://www.bbcnews.com?id=321
#2 x2 http://www.bbcnews2.com?id=321  http://google.com?id=1234       https://www.youtube/com
#4 x4        https://google.com/text https://bbcnews.com/search       www.youtube.com/searcht