r-通过乘法运算将字符串转换为数字

Question

我想用乘法运算符将字符串转换为数字。在我的数据帧mydf中，有一列ESPAC，我的想法是转换第一行，例如：；2.70x2.20"；使用CCD_ 3的操作。有简单的方法吗？我想要的最终输出是mydf2:

ID<-1:9
ESPAC<-c("2.70x2.20","3.5X2","3.6X2","3.00x1.33","3.00x2.00","3.00x2.50","3.00x3.00","3.5x2.14","3.90x2.32")
mydf<-data.frame(ID,ESPAC)
mydf
#  ID     ESPAC
#1  1 2.70x2.20
#2  2     3.5X2
#3  3     3.6X2
#4  4 3.00x1.33
#5  5 3.00x2.00
#6  6 3.00x2.50
#7  7 3.00x3.00
#8  8  3.5x2.14
#9  9 3.90x2.32
mydf2
#  ID     ESPAC
#1  1      5.9
#2  2      7.0
# ...
#9  9      9.0

Answer 1

在用*替换x后，您还可以使用eval、parse、text。

mydf$ESPAC <- sapply(gsub('x', '*', mydf$ESPAC, ignore.case = TRUE), 
function(x) eval(parse(text = x)))
mydf
#  ID ESPAC
#1  1 5.940
#2  2 7.000
#3  3 7.200
#4  4 3.990
#5  5 6.000
#6  6 7.500
#7  7 9.000
#8  8 7.490
#9  9 9.048

Answer 2

基R

mydf$res <- sapply(strsplit(mydf$ESPAC, "[Xx]"), function(z) prod(as.numeric(z)))
mydf
#   ID     ESPAC   res
# 1  1 2.70x2.20 5.940
# 2  2     3.5X2 7.000
# 3  3     3.6X2 7.200
# 4  4 3.00x1.33 3.990
# 5  5 3.00x2.00 6.000
# 6  6 3.00x2.50 7.500
# 7  7 3.00x3.00 9.000
# 8  8  3.5x2.14 7.490
# 9  9 3.90x2.32 9.048

dplyr

library(dplyr)
mydf %>%
mutate(res = sapply(strsplit(ESPAC, "[Xx]"), function(z) prod(as.numeric(z))))
#   ID     ESPAC   res
# 1  1 2.70x2.20 5.940
# 2  2     3.5X2 7.000
# 3  3     3.6X2 7.200
# 4  4 3.00x1.33 3.990
# 5  5 3.00x2.00 6.000
# 6  6 3.00x2.50 7.500
# 7  7 3.00x3.00 9.000
# 8  8  3.5x2.14 7.490
# 9  9 3.90x2.32 9.048

---

数据

mydf <- structure(list(ID = 1:9, ESPAC = c("2.70x2.20", "3.5X2", "3.6X2", "3.00x1.33", "3.00x2.00", "3.00x2.50", "3.00x3.00", "3.5x2.14", "3.90x2.32"), res = c(5.94, 7, 7.2, 3.99, 6, 7.5, 9, 7.49, 9.048)), row.names = c(NA, -9L), class = "data.frame")

Answer 3

我们可以在vectorized方式中做到这一点

library(dplyr)
library(tidyr)
mydf %>% 
separate(ESPAC, into = c('res', 'res2'), sep="[xX]", 
convert = TRUE, remove = FALSE) %>% 
mutate(res = res * res2, res2 = NULL)
ID     ESPAC   res
1  1 2.70x2.20 5.940
2  2     3.5X2 7.000
3  3     3.6X2 7.200
4  4 3.00x1.33 3.990
5  5 3.00x2.00 6.000
6  6 3.00x2.50 7.500
7  7 3.00x3.00 9.000
8  8  3.5x2.14 7.490
9  9 3.90x2.32 9.048

---

或使用base R和read.table

mydf$res <- Reduce(`*`, read.table(text = sub("x", "X", mydf$ESPAC), 
header = FALSE, sep="X"))

数据

mydf <- structure(list(ID = 1:9, ESPAC = c("2.70x2.20", "3.5X2", "3.6X2", 
"3.00x1.33", "3.00x2.00", "3.00x2.50", "3.00x3.00", "3.5x2.14", 
"3.90x2.32"), res = c(5.94, 7, 7.2, 3.99, 6, 7.5, 9, 7.49, 9.048
)), row.names = c(NA, -9L), class = "data.frame")