[英]Use a regular expression extract substring from data frame columns in R
I am fairly new to R so please go easy on me if this is a stupid question. 我对R相当陌生,所以如果这是一个愚蠢的问题,请对我轻松一点。
I have a dataframe called foo
: 我有一个名为
foo
的数据框:
< head(foo)
Old.Clone.Name New.Clone.Name File
1 A Aa A_mask_MF_final_IS2_SAEE7-1_02.nrrd
2 B Bb B_mask_MF_final_IS2ViaIS2h_SADQ15-1_02.nrrd
3 C Cc C_mask_MF_final_IS2ViaIS2h_SAEC16-1_02.nrrd
4 D Dd D_mask_MF_final_IS2ViaIS2h_SAEJ6-1_02.nrrd
5 E Ee F_mask_MF_final_IS2_SAED9-1_02.nrrd
6 F Ff F_mask_MF_final_IS2ViaIS2h_SAGP3-1_02.nrrd
I want to extract codes from the File
column that match the regular expression (S[AZ]{3}[0-9]{1,2}-[0-9]_02)
, to give me: 我想从“
File
列中提取与正则表达式(S[AZ]{3}[0-9]{1,2}-[0-9]_02)
相匹配的代码,以便给我:
SAEE7-1_02
SADQ15-1_02
SAEC16-1_02
SAEJ6-1_02
SAED9-1_02
SAGP3-1_02
I then want to use these codes to search another directory for other files that contain the same code. 然后,我想使用这些代码在另一个目录中搜索包含相同代码的其他文件。
I fail, however, at the first hurdle and cannot extract the codes from that column of the data frame. 但是,我首先遇到了困难,无法从数据帧的该列中提取代码。
I have tried: 我努力了:
library('stringr')
str_extract(foo[3],regex("(S[A-Z]{3}[0-9]{1,2}-[0-9]_02)", ignore_case = TRUE))
but this just returns [1] NA
. 但这只返回
[1] NA
。
Am I simply missing something obvious? 我只是缺少明显的东西吗? I look forward to cracking this with a bit of help from the community.
我期待在社区的帮助下破解此问题。
Hello if you are reading the data as a table file then foo[3]
is a list and str_extract does not accept lists, only strings, then you should use lapply to extract the match of every element. 您好,如果您将数据作为表文件读取,则
foo[3]
是一个列表,而str_extract不接受列表,仅接受字符串,那么您应该使用lapply提取每个元素的匹配项。
lapply(foo[3], function(x) str_extract(x, "[sS][a-zA-Z]{3}[0-9]{1,2}-[0-9]_02"))
Result: 结果:
[1] "SAEE7-1_02" "SADQ15-1_02" "SAEC16-1_02" "SAEJ6-1_02" "SAED9-1_02"
[6] "SAGP3-1_02"
str_extract(foo[3],"(?i)S[A-Z]{3}[0-9]{1,2}-[0-9]_02")
seems to work. 似乎有效。 Somehow, my R gave me
不知何故,我的R给了我
"Error in check_pattern(pattern, string) : could not find function "regex""
“ check_pattern(pattern,string)中的错误:找不到函数“ regex””
when using your original expression. 使用原始表达时。
The following code will repeat what you asked (just copy and paste to your R console ): 以下代码将重复您的要求(只需复制并粘贴到R控制台中 ):
library(stringr)
foo = scan(what='')
Old.Clone.Name New.Clone.Name File
A Aa A_mask_MF_final_IS2_SAEE7-1_02.nrrd
B Bb B_mask_MF_final_IS2ViaIS2h_SADQ15-1_02.nrrd
C Cc C_mask_MF_final_IS2ViaIS2h_SAEC16-1_02.nrrd
D Dd D_mask_MF_final_IS2ViaIS2h_SAEJ6-1_02.nrrd
E Ee F_mask_MF_final_IS2_SAED9-1_02.nrrd
F Ff F_mask_MF_final_IS2ViaIS2h_SAGP3-1_02.nrrd
foo = matrix(foo,ncol=3,byrow=T)
colnames(foo)=foo[1,]
foo = foo[-1,]
foo
str_extract(foo[,3],regex("(S[A-Z]{3}[0-9]{1,2}-[0-9]_02)", ignore_case = T))
The reason you get NULL is hidden: R stores entries by column, hence foo[3]
is the 3rd row and 1st column of foo matrix/data frame. 您得到NULL的原因是隐藏的:R按列存储条目,因此
foo[3]
是foo矩阵/数据帧的第3行和第1列。 To quote the third column, you may need to use foo[,3]
. 要引用第三列,您可能需要使用
foo[,3]
。 or foo<-data.frame(foo); foo[[3]]
或
foo<-data.frame(foo); foo[[3]]
foo<-data.frame(foo); foo[[3]]
. foo<-data.frame(foo); foo[[3]]
。
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