R,使用read.csv一步读入字符作为数字？

Question

我正在将.csv读入带有几种不同变量类型的R中,其中两种作为字符读入,尽管它们是数字的(十进制度数的纬度和经度).为了解决这个问题,我在阅读之后将它们定义为"as.numeric".有更优雅的方法吗？也许在"read.csv"的调用中？

d <- read.csv("data.csv",stringsAsFactors=F)
> str(d)
'data.frame':   467674 obs. of  7 variables:
 $ station     : chr  "USC00036506" "USC00036506" "USC00036506" "USC00036506" ...
 $ station_name: chr  "SEARCY AR US" "SEARCY AR US" "SEARCY AR US" "SEARCY AR US" ...
 $ lat         : chr  "35.25" "35.25" "35.25" "35.25" ...
 $ lon         : chr  "-91.75" "-91.75" "-91.75" "-91.75" ...
 $ tmax        : int  50 50 39 100 72 61 -17 -44 6 0 ...
 $ tmin        : int  -39 -39 -89 -61 -6 -83 -144 -150 -161 -128 ...
 $ tobs        : int  33 22 17 61 61 -78 -50 -94 -22 -11 ...

d$lat <- as.numeric(d$lat)
d$lon <- as.numeric(d$lon)

> str(d)
'data.frame':   467674 obs. of  7 variables:
 $ station     : chr  "USC00036506" "USC00036506" "USC00036506" "USC00036506" ...
 $ station_name: chr  "SEARCY AR US" "SEARCY AR US" "SEARCY AR US" "SEARCY AR US" ...
 $ lat         : num  35.2 35.2 35.2 35.2 35.2 ...
 $ lon         : num  -91.8 -91.8 -91.8 -91.8 -91.8 ...
 $ tmax        : int  50 50 39 100 72 61 -17 -44 6 0 ...
 $ tmin        : int  -39 -39 -89 -61 -6 -83 -144 -150 -161 -128 ...
 $ tobs        : int  33 22 17 61 61 -78 -50 -94 -22 -11 ...

Answer 1

您可以设置列类.试试这个:

cls <- c(lat="numeric", lon="numeric")
read.csv("data.csv", colClasses=cls, stringsAsFactors=FALSE)

注意:未经测试,因为您不提供测试数据.