通过逻辑索引向量设置列表

Question

我有一个复杂列表，需要根据布尔元素的值从其中选择一个子集(我需要具有hidden值等于FALSE的记录)。我尝试了以下基于索引向量的代码，但是失败了(如这个输出的末尾所示)：

startups <- data$startups[data$startups$hidden == FALSE]

或者，另一种选择是：

startups <- data$startups[!as.logical(data$startups$hidden)]

互动R会议证明数据在那里：

Browse[1]> str(data$startups, list.len=3)
List of 50
 $ :List of 23
  ..$ id               : num 357496
  ..$ hidden           : logi FALSE
  ..$ community_profile: logi FALSE
  .. [list output truncated]
 $ :List of 2
  ..$ id    : num 352159
  ..$ hidden: logi TRUE
 $ :List of 2
  ..$ id    : num 352157
  ..$ hidden: logi TRUE
  [list output truncated]

Browse[1]> data$startups[data$startups$hidden == FALSE]
list()

Browse[1]> data$startups[!as.logical(data$startups$hidden)]
list()

我的代码有什么问题？

更新(希望包括可重复的示例，抱歉，复杂的结构)

aa <- dput(head(data$startups, n=3))

产生以下输出：

list(structure(list(id = 386938, hidden = FALSE, community_profile = FALSE, 
    name = "Pritunl", angellist_url = "https://angel.co/pritunl", 
    logo_url = "https://s3.amazonaws.com/photos.angel.co/startups/i/386938-fac0b8cba76c7e9252eee6646ec5b681-medium_jpg.jpg?buster=1398401450", 
    thumb_url = "https://s3.amazonaws.com/photos.angel.co/startups/i/386938-fac0b8cba76c7e9252eee6646ec5b681-thumb_jpg.jpg?buster=1398401450", 
    quality = 0, product_desc = "Enterprise VPN/cloud networking server", 
    high_concept = "Enterprise cloud networking", follower_count = 1, 
    company_url = "http://pritunl.com", created_at = "2014-04-25T04:50:57Z", 
    updated_at = "2014-04-25T06:02:05Z", crunchbase_url = NULL, 
    twitter_url = "http://twitter.com/pritunl", blog_url = "", 
    video_url = "", markets = list(structure(list(id = 12, tag_type = "MarketTag", 
        name = "enterprise software", display_name = "Enterprise Software", 
        angellist_url = "https://angel.co/enterprise-software"), .Names = c("id", 
    "tag_type", "name", "display_name", "angellist_url")), structure(list(
        id = 59, tag_type = "MarketTag", name = "open source", 
        display_name = "Open Source", angellist_url = "https://angel.co/open-source"), .Names = c("id", 
    "tag_type", "name", "display_name", "angellist_url")), structure(list(
        id = 123, tag_type = "MarketTag", name = "internet infrastructure", 
        display_name = "Internet Infrastructure", angellist_url = "https://angel.co/internet-infrastructure"), .Names = c("id", 
    "tag_type", "name", "display_name", "angellist_url")), structure(list(
        id = 306, tag_type = "MarketTag", name = "cloud management", 
        display_name = "Cloud Management", angellist_url = "https://angel.co/cloud-management"), .Names = c("id", 
    "tag_type", "name", "display_name", "angellist_url"))), locations = list(
        structure(list(id = 2071, tag_type = "LocationTag", name = "new york", 
            display_name = "New York", angellist_url = "https://angel.co/new-york"), .Names = c("id", 
        "tag_type", "name", "display_name", "angellist_url"))), 
    company_size = "1-10", company_type = list(structure(list(
        id = 94212, tag_type = "CompanyTypeTag", name = "startup", 
        display_name = "Startup", angellist_url = "https://angel.co/startup"), .Names = c("id", 
    "tag_type", "name", "display_name", "angellist_url"))), status = NULL, 
    screenshots = list(structure(list(thumb = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/5f7410543201d583eaba1975b931f3fd-thumb_jpg.jpg", 
        original = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/5f7410543201d583eaba1975b931f3fd-original.png"), .Names = c("thumb", 
    "original")), structure(list(thumb = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/006c4fb50d4b10df7caf7800ee482c6b-thumb_jpg.jpg", 
        original = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/006c4fb50d4b10df7caf7800ee482c6b-original.png"), .Names = c("thumb", 
    "original")), structure(list(thumb = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/741225c3de5021399c0cfc33cecb8830-thumb_jpg.jpg", 
        original = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/741225c3de5021399c0cfc33cecb8830-original.png"), .Names = c("thumb", 
    "original")), structure(list(thumb = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/969b60b6ccda577e77b7c9a5c169b2fd-thumb_jpg.jpg", 
        original = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/969b60b6ccda577e77b7c9a5c169b2fd-original.png"), .Names = c("thumb", 
    "original")), structure(list(thumb = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/2b2cc3a046c5a4d20b328045ca7f0254-thumb_jpg.jpg", 
        original = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/2b2cc3a046c5a4d20b328045ca7f0254-original.png"), .Names = c("thumb", 
    "original")), structure(list(thumb = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/053c3a1c74fc7f39de1117770f9debef-thumb_jpg.jpg", 
        original = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/053c3a1c74fc7f39de1117770f9debef-original.png"), .Names = c("thumb", 
    "original")), structure(list(thumb = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/8adcf2d6a6cafc9c6b810f8359a3fedf-thumb_jpg.jpg", 
        original = "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/8adcf2d6a6cafc9c6b810f8359a3fedf-original.png"), .Names = c("thumb", 
    "original")))), .Names = c("id", "hidden", "community_profile", 
"name", "angellist_url", "logo_url", "thumb_url", "quality", 
"product_desc", "high_concept", "follower_count", "company_url", 
"created_at", "updated_at", "crunchbase_url", "twitter_url", 
"blog_url", "video_url", "markets", "locations", "company_size", 
"company_type", "status", "screenshots")), structure(list(id = 385596, 
    hidden = FALSE, community_profile = TRUE, name = "Lariat ", 
    angellist_url = "https://angel.co/lariat-1", logo_url = "https://s3.amazonaws.com/photos.angel.co/startups/i/385596-29de05d584176c3972da411aed5485f0-medium_jpg.jpg?buster=1398260121", 
    thumb_url = "https://s3.amazonaws.com/photos.angel.co/startups/i/385596-29de05d584176c3972da411aed5485f0-thumb_jpg.jpg?buster=1398260121", 
    quality = 0, product_desc = "Thus far, the internet has gone from discovery to search discovery, and then social discovery, but with little focus on recall. Remembering your digital footprint is difficult. We aim to solve that problem. Lariat is a cloud-based recall engine to securely recall information from any page in your search history instantly through intuitive keyword search, not just from page titles, but from the contents and context of the underlying pages.\r\n\r\nWrangle in the information you want, easier and faster.", 
    high_concept = "Recall your digital footprint on the web instantly", 
    follower_count = 1, company_url = "http://www.lariattech.com", 
    created_at = "2014-04-23T13:17:47Z", updated_at = "2014-04-23T13:48:38Z", 
    crunchbase_url = NULL, twitter_url = "", blog_url = "", video_url = NULL, 
    markets = list(structure(list(id = 4, tag_type = "MarketTag", 
        name = "digital media", display_name = "Digital Media", 
        angellist_url = "https://angel.co/digital-media"), .Names = c("id", 
    "tag_type", "name", "display_name", "angellist_url")), structure(list(
        id = 12, tag_type = "MarketTag", name = "enterprise software", 
        display_name = "Enterprise Software", angellist_url = "https://angel.co/enterprise-software"), .Names = c("id", 
    "tag_type", "name", "display_name", "angellist_url")), structure(list(
        id = 59, tag_type = "MarketTag", name = "open source", 
        display_name = "Open Source", angellist_url = "https://angel.co/open-source"), .Names = c("id", 
    "tag_type", "name", "display_name", "angellist_url")), structure(list(
        id = 282, tag_type = "MarketTag", name = "semantic search", 
        display_name = "Semantic Search", angellist_url = "https://angel.co/semantic-search"), .Names = c("id", 
    "tag_type", "name", "display_name", "angellist_url"))), locations = list(
        structure(list(id = 1620, tag_type = "LocationTag", name = "boston", 
            display_name = "Boston", angellist_url = "https://angel.co/boston"), .Names = c("id", 
        "tag_type", "name", "display_name", "angellist_url"))), 
    company_size = "1-10", company_type = structure(list(), class = "AsIs"), 
    status = NULL, screenshots = structure(list(), class = "AsIs")), .Names = c("id", 
"hidden", "community_profile", "name", "angellist_url", "logo_url", 
"thumb_url", "quality", "product_desc", "high_concept", "follower_count", 
"company_url", "created_at", "updated_at", "crunchbase_url", 
"twitter_url", "blog_url", "video_url", "markets", "locations", 
"company_size", "company_type", "status", "screenshots")), structure(list(
    id = 385595, hidden = TRUE), .Names = c("id", "hidden")))

同样的格式(aa)也是如此：

[[1]]
[[1]]$id
[1] 386938

[[1]]$hidden
[1] FALSE

[[1]]$community_profile
[1] FALSE

[[1]]$name
[1] "Pritunl"

[[1]]$angellist_url
[1] "https://angel.co/pritunl"

[[1]]$logo_url
[1] "https://s3.amazonaws.com/photos.angel.co/startups/i/386938-fac0b8cba76c7e9252eee6646ec5b681-medium_jpg.jpg?buster=1398401450"

[[1]]$thumb_url
[1] "https://s3.amazonaws.com/photos.angel.co/startups/i/386938-fac0b8cba76c7e9252eee6646ec5b681-thumb_jpg.jpg?buster=1398401450"

[[1]]$quality
[1] 0

[[1]]$product_desc
[1] "Enterprise VPN/cloud networking server"

[[1]]$high_concept
[1] "Enterprise cloud networking"

[[1]]$follower_count
[1] 1

[[1]]$company_url
[1] "http://pritunl.com"

[[1]]$created_at
[1] "2014-04-25T04:50:57Z"

[[1]]$updated_at
[1] "2014-04-25T06:02:05Z"

[[1]]$crunchbase_url
NULL

[[1]]$twitter_url
[1] "http://twitter.com/pritunl"

[[1]]$blog_url
[1] ""

[[1]]$video_url
[1] ""

[[1]]$markets
[[1]]$markets[[1]]
[[1]]$markets[[1]]$id
[1] 12

[[1]]$markets[[1]]$tag_type
[1] "MarketTag"

[[1]]$markets[[1]]$name
[1] "enterprise software"

[[1]]$markets[[1]]$display_name
[1] "Enterprise Software"

[[1]]$markets[[1]]$angellist_url
[1] "https://angel.co/enterprise-software"


[[1]]$markets[[2]]
[[1]]$markets[[2]]$id
[1] 59

[[1]]$markets[[2]]$tag_type
[1] "MarketTag"

[[1]]$markets[[2]]$name
[1] "open source"

[[1]]$markets[[2]]$display_name
[1] "Open Source"

[[1]]$markets[[2]]$angellist_url
[1] "https://angel.co/open-source"


[[1]]$markets[[3]]
[[1]]$markets[[3]]$id
[1] 123

[[1]]$markets[[3]]$tag_type
[1] "MarketTag"

[[1]]$markets[[3]]$name
[1] "internet infrastructure"

[[1]]$markets[[3]]$display_name
[1] "Internet Infrastructure"

[[1]]$markets[[3]]$angellist_url
[1] "https://angel.co/internet-infrastructure"


[[1]]$markets[[4]]
[[1]]$markets[[4]]$id
[1] 306

[[1]]$markets[[4]]$tag_type
[1] "MarketTag"

[[1]]$markets[[4]]$name
[1] "cloud management"

[[1]]$markets[[4]]$display_name
[1] "Cloud Management"

[[1]]$markets[[4]]$angellist_url
[1] "https://angel.co/cloud-management"



[[1]]$locations
[[1]]$locations[[1]]
[[1]]$locations[[1]]$id
[1] 2071

[[1]]$locations[[1]]$tag_type
[1] "LocationTag"

[[1]]$locations[[1]]$name
[1] "new york"

[[1]]$locations[[1]]$display_name
[1] "New York"

[[1]]$locations[[1]]$angellist_url
[1] "https://angel.co/new-york"



[[1]]$company_size
[1] "1-10"

[[1]]$company_type
[[1]]$company_type[[1]]
[[1]]$company_type[[1]]$id
[1] 94212

[[1]]$company_type[[1]]$tag_type
[1] "CompanyTypeTag"

[[1]]$company_type[[1]]$name
[1] "startup"

[[1]]$company_type[[1]]$display_name
[1] "Startup"

[[1]]$company_type[[1]]$angellist_url
[1] "https://angel.co/startup"



[[1]]$status
NULL

[[1]]$screenshots
[[1]]$screenshots[[1]]
[[1]]$screenshots[[1]]$thumb
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/5f7410543201d583eaba1975b931f3fd-thumb_jpg.jpg"

[[1]]$screenshots[[1]]$original
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/5f7410543201d583eaba1975b931f3fd-original.png"


[[1]]$screenshots[[2]]
[[1]]$screenshots[[2]]$thumb
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/006c4fb50d4b10df7caf7800ee482c6b-thumb_jpg.jpg"

[[1]]$screenshots[[2]]$original
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/006c4fb50d4b10df7caf7800ee482c6b-original.png"


[[1]]$screenshots[[3]]
[[1]]$screenshots[[3]]$thumb
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/741225c3de5021399c0cfc33cecb8830-thumb_jpg.jpg"

[[1]]$screenshots[[3]]$original
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/741225c3de5021399c0cfc33cecb8830-original.png"


[[1]]$screenshots[[4]]
[[1]]$screenshots[[4]]$thumb
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/969b60b6ccda577e77b7c9a5c169b2fd-thumb_jpg.jpg"

[[1]]$screenshots[[4]]$original
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/969b60b6ccda577e77b7c9a5c169b2fd-original.png"


[[1]]$screenshots[[5]]
[[1]]$screenshots[[5]]$thumb
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/2b2cc3a046c5a4d20b328045ca7f0254-thumb_jpg.jpg"

[[1]]$screenshots[[5]]$original
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/2b2cc3a046c5a4d20b328045ca7f0254-original.png"


[[1]]$screenshots[[6]]
[[1]]$screenshots[[6]]$thumb
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/053c3a1c74fc7f39de1117770f9debef-thumb_jpg.jpg"

[[1]]$screenshots[[6]]$original
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/053c3a1c74fc7f39de1117770f9debef-original.png"


[[1]]$screenshots[[7]]
[[1]]$screenshots[[7]]$thumb
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/8adcf2d6a6cafc9c6b810f8359a3fedf-thumb_jpg.jpg"

[[1]]$screenshots[[7]]$original
[1] "https://s3.amazonaws.com/screenshots.angel.co/ae/386938/8adcf2d6a6cafc9c6b810f8359a3fedf-original.png"




[[2]]
[[2]]$id
[1] 385596

[[2]]$hidden
[1] FALSE

[[2]]$community_profile
[1] TRUE

[[2]]$name
[1] "Lariat "

[[2]]$angellist_url
[1] "https://angel.co/lariat-1"

[[2]]$logo_url
[1] "https://s3.amazonaws.com/photos.angel.co/startups/i/385596-29de05d584176c3972da411aed5485f0-medium_jpg.jpg?buster=1398260121"

[[2]]$thumb_url
[1] "https://s3.amazonaws.com/photos.angel.co/startups/i/385596-29de05d584176c3972da411aed5485f0-thumb_jpg.jpg?buster=1398260121"

[[2]]$quality
[1] 0

[[2]]$product_desc
[1] "Thus far, the internet has gone from discovery to search discovery, and then social discovery, but with little focus on recall. Remembering your digital footprint is difficult. We aim to solve that problem. Lariat is a cloud-based recall engine to securely recall information from any page in your search history instantly through intuitive keyword search, not just from page titles, but from the contents and context of the underlying pages.\r\n\r\nWrangle in the information you want, easier and faster."

[[2]]$high_concept
[1] "Recall your digital footprint on the web instantly"

[[2]]$follower_count
[1] 1

[[2]]$company_url
[1] "http://www.lariattech.com"

[[2]]$created_at
[1] "2014-04-23T13:17:47Z"

[[2]]$updated_at
[1] "2014-04-23T13:48:38Z"

[[2]]$crunchbase_url
NULL

[[2]]$twitter_url
[1] ""

[[2]]$blog_url
[1] ""

[[2]]$video_url
NULL

[[2]]$markets
[[2]]$markets[[1]]
[[2]]$markets[[1]]$id
[1] 4

[[2]]$markets[[1]]$tag_type
[1] "MarketTag"

[[2]]$markets[[1]]$name
[1] "digital media"

[[2]]$markets[[1]]$display_name
[1] "Digital Media"

[[2]]$markets[[1]]$angellist_url
[1] "https://angel.co/digital-media"


[[2]]$markets[[2]]
[[2]]$markets[[2]]$id
[1] 12

[[2]]$markets[[2]]$tag_type
[1] "MarketTag"

[[2]]$markets[[2]]$name
[1] "enterprise software"

[[2]]$markets[[2]]$display_name
[1] "Enterprise Software"

[[2]]$markets[[2]]$angellist_url
[1] "https://angel.co/enterprise-software"


[[2]]$markets[[3]]
[[2]]$markets[[3]]$id
[1] 59

[[2]]$markets[[3]]$tag_type
[1] "MarketTag"

[[2]]$markets[[3]]$name
[1] "open source"

[[2]]$markets[[3]]$display_name
[1] "Open Source"

[[2]]$markets[[3]]$angellist_url
[1] "https://angel.co/open-source"


[[2]]$markets[[4]]
[[2]]$markets[[4]]$id
[1] 282

[[2]]$markets[[4]]$tag_type
[1] "MarketTag"

[[2]]$markets[[4]]$name
[1] "semantic search"

[[2]]$markets[[4]]$display_name
[1] "Semantic Search"

[[2]]$markets[[4]]$angellist_url
[1] "https://angel.co/semantic-search"



[[2]]$locations
[[2]]$locations[[1]]
[[2]]$locations[[1]]$id
[1] 1620

[[2]]$locations[[1]]$tag_type
[1] "LocationTag"

[[2]]$locations[[1]]$name
[1] "boston"

[[2]]$locations[[1]]$display_name
[1] "Boston"

[[2]]$locations[[1]]$angellist_url
[1] "https://angel.co/boston"



[[2]]$company_size
[1] "1-10"

[[2]]$company_type
list()

[[2]]$status
NULL

[[2]]$screenshots
list()


[[3]]
[[3]]$id
[1] 385595

[[3]]$hidden
[1] TRUE

最后，通过逻辑索引向量应用子设置操作：

aa[data$startups$hidden == FALSE]

结果是一个空列表(尽管第1和第2元素为hidden = FALSE )：

list()

同样，对于输出的大小很抱歉，但是我不得不保留列表的结构。

Considerations:

根据R项目的“R简介”(http://cran.r-project.org/doc/manuals/R-intro.html#Index-vectors)，

“向量的元素子集可以通过在向量的名称后面加上方括号中的索引向量来选择。更普遍的是，任何计算为向量的表达式都可能具有类似的元素子集，即在表达式后面加上方括号中的索引向量。”

A同时，根据哈德利韦翰的“高级R”(http://adv-r.had.co.nz/Subsetting.html)，

“删除列表的工作方式与删除原子向量的方式完全相同”。

Answer 1

问题中的示例数据是一个长度为3的列表，我们称之为L。它的每个组件本身就是一个列表，每个子列表中的一个组件是hidden。我们可以将子列表的hidden组件提取到一个名为hidden的逻辑向量中。使用该逻辑向量，我们可以子集原始列表L，给出一个新列表，其中只包含带有hidden组件的TRUE的子列表。

hidden <- sapply(L, "[[", "hidden") # create logical vector hidden
L[hidden]

对于提供的数据，我们得到一个包含一个组件的列表：

> length(L[hidden])
[1] 1

如果我们知道只有一个组件，那么L[hidden][[1]]或L[[which(hidden)]]就会给出这个组件。

Answer 2

数据帧使用两个数字进行索引。要只选择行，需要执行以下操作：

data$startups[data$startups$hidden == FALSE, ]