如何计算一列字符串的每行中给定字符的出现次数? [英] How to calculate the number of occurrence of a given character in each row of a column of strings?
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问题描述
示例:
q.data< -data.frame(number = 1:3,string = c(greatgreat,magic,not))
我想为q.data创建一个新列,字符串中出现a的数目(即c(2,1, 0))。
我所管理的唯一复杂的方法是:
string.counter< -function(strings,pattern){
计数< -NULL
for(i in 1:length(strings)){
计数[i] (attr(greerxpr(pattern,strings [i])[[1]],match.length)> 0])
}
返回(计数)
}
string.counter(strings = q.data $ string,pattern =a)
number string number.of.a
1 1 greatgreat 2
2 2魔术1
3 3不是0
解决方案
stringr包提供 str_count
函数,这似乎是您感兴趣的
#加载您的示例数据
q.data< -data.frame(number = 1:3,string = c(greatgreat,magic 否),stringsAsFactors = F)
库(stringr)
#计算字符串
的每个元素中的a的数量q.data $ number.of.a < - str_count(q.data $ string,a)
q.data
#number string number.of.a
#1 1 greatgreat 2
#2 2魔术1
#3 3不0
I have a data.frame in which certain variables contain a text string. I wish to count the number of occurrences of a given character in each individual string.
Example:
q.data<-data.frame(number=1:3, string=c("greatgreat", "magic", "not"))
I wish to create a new column for q.data with the number of occurence of "a" in string (ie. c(2,1,0)).
The only convoluted approach I have managed is:
string.counter<-function(strings, pattern){
counts<-NULL
for(i in 1:length(strings)){
counts[i]<-length(attr(gregexpr(pattern,strings[i])[[1]], "match.length")[attr(gregexpr(pattern,strings[i])[[1]], "match.length")>0])
}
return(counts)
}
string.counter(strings=q.data$string, pattern="a")
number string number.of.a
1 1 greatgreat 2
2 2 magic 1
3 3 not 0
解决方案
The stringr package provides the str_count
function which seems to do what you're interested in
# Load your example data
q.data<-data.frame(number=1:3, string=c("greatgreat", "magic", "not"), stringsAsFactors = F)
library(stringr)
# Count the number of 'a's in each element of string
q.data$number.of.a <- str_count(q.data$string, "a")
q.data
# number string number.of.a
#1 1 greatgreat 2
#2 2 magic 1
#3 3 not 0
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