string R - 在包含字符串的字符数组中查找元素
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R - find elements in a character array that contains a string
提问by Se?or O
I want to extract the elements of a character array that contains some particular string. For example:
我想提取包含某些特定字符串的字符数组的元素。例如：
x <- c('aa', 'ab', 'ac', 'bb', 'bc')
I want some function such that, given xand 'a'(in general this can be a string), it returns 'aa', 'ab', 'ac'. I have experimented with a combination of %in%, match, which, etc, but have not been able to make them work. Any idea?
我想要一些函数，这样，给定x和'a'（通常这可以是一个字符串），它返回'aa', 'ab', 'ac'. 我已经尝试的组合%in%，match，which等，但一直无法让他们的工作。任何的想法？
回答by Se?or O
Just use grep:
只需使用grep：
grep('a', x, value=TRUE)
[1] "aa" "ab" "ac"
回答by Hanif
In a table or a list, we can use dplyr::pull from dplyr/tidyverse package to convert values in a column to a vector first and then find the particular value in the column. For instance, in the LEGO example, we can do the following to find any theme starting by "s" or "S":
在表格或列表中，我们可以使用 dplyr/tidyverse 包中的 dplyr::pull 将列中的值先转换为向量，然后在列中找到特定的值。例如，在乐高示例中，我们可以执行以下操作来查找以“s”或“S”开头的任何主题：
inventory_parts_themes <- inventories %>%
inner_join(inventory_parts, by = c("id" = "inventory_id")) %>%
arrange(desc(quantity)) %>%
select(-id, -version) %>%
inner_join(sets, by = "set_num") %>%
inner_join(themes, by = c("theme_id" = "id"), suffix = c("_set", "_theme"))
all_theme_names <- dplyr::pull(inventory_parts_themes, name_theme)
all_theme_names[grep("^[sS].*", all_theme_names)]
