使用data.table的字符串匹配不完美 [英] Imperfect string match using data.table

问题描述

好，所以不久前我发布了一个问题，该问题涉及编写R函数来加速大型文本文件的字符串匹配。我睁开了眼睛对 data.table，问题得到了很好的回答。

Ok, so I posted a question a while back concerning writing an R function to accelerate string matching of large text files. I had my eyes opened to 'data.table' and my question was answered perfectly.

这是指向该线程的链接，其中包括所有数据和详细信息：

This is the link to that thread which includes all of the data and details:

加快R中字符串匹配的性能和速度

但是现在我遇到了另一个问题。有时，提交的VIN＃（在 vinDB文件中）在 carFile文件中相差一个或两个字符，这是由于在DMV上填写汽车信息时由于人为错误所致。有没有办法编辑

But now I am running into another problem. Once in a while, the submitted VIN#s (in the 'vinDB' file) differ by one or two characters in the 'carFile' file due to human error when they fill out their car info at the DMV. Is there a way to edit the

dt[J(car.vins), list(NumTimesFound=.N), by=vin.names]

该代码行（由上述链接中的@BrodieG提供）以允许识别一个或两个字符不同的VIN＃？

line of that code (provided by @BrodieG in the above link) to allow for a recognition of VIN#s that differ by one or two characters?

很抱歉，这很容易纠正。我只是对R中 data.table包的强大功能感到不知所措，并希望尽可能多地学习其实用程序，并且该论坛的知识渊博的成员对我来说绝对至关重要。

I apologize if this is an easy correction. I am just overwhelmed by the power of the 'data.table' package in R and would love to learn as much as I can of its utility, and the knowledgable members of this forum have been absolutely pivotal to me.

**编辑：

所以我一直在使用'lapply'和'agrep'功能已建议，我必须做错了什么：

So I have been playing around with using 'lapply' and the 'agrep' functions as suggested and I must be doing something wrong:

我尝试替换此行：

dt[J(car.vins), list(NumTimesFound=.N), by=vin.names]

与此：

dt <- dt[lapply(vin.vins, function(x) agrep(x,car.vins, max.distance=2)), list(NumTimesFound=.N), vin.names, allow.cartesian=TRUE]

但出现以下错误：

Error in `[.data.table`(dt, lapply(vin.vins, function(x) agrep(x,car.vins,  : 
x.'vin.vins' is a character column being joined to i.'V1' which is type 'integer'. 
Character columns must join to factor or character columns.

都是'chr'类型，有人知道我为什么会收到此错误吗，我是否正在以正确的方式考虑，即：我在使用l

But they are both type 'chr'. Does anyone know why I am getting this error? And am I thinking about this the right way, ie: am I using lapply correctly here?

谢谢！

推荐答案

我终于明白了！ 。

agrep 函数的值选项需要从 FALSE （默认）更改为 TRUE ：

The agrep-function has a value-option that needs to be altered from FALSE (default) to TRUE:

dt <- dt[lapply(car.vins, agrep, x = vin.vins, max.distance = c(cost=2, all=2), value = TRUE)
         , .(NumTimesFound = .N)
         , by = vin.names]

注意：最大距离参数可以根据Levenshtein距离，替换，删除等进行更改。 agrep是一种引人入胜的功能！

Note: the max.distance parameters can be altered based on Levenshtein distance, substitutions, deletions, etc. 'agrep' is a fascinating function!

再次感谢为所有的帮助！

Thanks again for all the help!

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