如何在data.table中进行负/ nomatch /反向搜索？

本文介绍了如何在data.table中进行负/ nomatch /反向搜索？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 29岁程序员，3月因学历无情被辞！ 如果我想选择data.table中的所有行，在关键变量中不包含特定值使用二叉搜索会发生什么？顺便问一下，我想做什么是正确的行话？是nojoin吗？是否为否定选择？ DT = data.table（x = rep（c（a，b ，c），每个= 3），y = c（1,3,6），v = 1：9） setkey（DT，x） / pre> 允许对所有x ==a行使用二进制搜索进行肯定选择 DT [a] 相反。我想要所有不是a的行，其中x！=a DT [x！= a] 这是一个矢量扫描。上面的行工作，但使用矢量扫描。我想使用二进制。我期待下面的工作，但唉... DT [！a] DT [ - a] 上面两个不工作，试图和nomatch一起玩， 解决方案这个习语是这样的： DT [-DT [a，which = TRUE]] xyv 1：b 1 4 2：b 3 5 3： b 6 6 4：c 1 7 5：c 3 8 6：c 6 9 灵感来源： 邮寄名单张贴返回选择/加入不匹配？ 上一个问题不与data.tables非联接 Matthew Dowle的 answer 到将R的数据框移植到数据表：如何识别重复的行？ 更新。 v1.8.3中的新增内容是非连接语法。 Farrel的第一个期望（！而不是 - ）已经实现： DT [-DT [a，which = TRUE，nomatch = 0]，...]＃old idiom DT [！ ..]＃相同的结果，现在首选。 请参阅 NEWS item for more detailed information and example。 What happens if I want to select all the rows in a data.table that do not contain a particular value in the key variable using binary search? By the way, what is the correct jargon for what I want to do? Is it "nojoin"? Is it "negative selection"?DT = data.table(x=rep(c("a","b","c"),each=3), y=c(1,3,6), v=1:9)setkey(DT,x)Lets do a positive selection for all rows where x=="a" but using binary searchDT["a"]That's beautiful but I want the opposite of that. I want all the rows that are not "a" in other words where x!="a"DT[x!="a"]That is a vector scanning. The above line works but is uses vector scanning. I want to use binary. I was expecting the following to work, but alas...DT[!"a"]DT[-"a"]The above two do not work and trying to play with nomatch got me nowhere. 解决方案 The idiom is this:DT[-DT["a", which=TRUE]] x y v1: b 1 42: b 3 53: b 6 64: c 1 75: c 3 86: c 6 9Inspiration from:The mailing list posting Return Select/Join that does NOT match?The previous question non-joins with data.tablesMatthew Dowle's answer to Porting set operations from R's data frames to data tables: How to identify duplicated rows?Update. New in v1.8.3 is not-join syntax. Farrel's first expectation (! rather than -) has been implemented :DT[-DT["a",which=TRUE,nomatch=0],...] # old idiomDT[!"a",...] # same result, now preferred.See the NEWS item for more detailed info and example. 这篇关于如何在data.table中进行负/ nomatch /反向搜索？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！