无法将字符转换为R中的数字

问题描述

我从以下“地下天气”网站复制并粘贴了天气信息，以进行一些数据分析，数据如下所示：

https://www.wunderground.com/dashboard/pws/KCACHINO13/table/2018-04-10/2018-04-10/daily

如您所见，温度和其他信息均带有文字，因此我无法进行任何计算。在excel中，我使用了replace（xx，“ F”，“”）从“ Temperature”列中删除了F，但是后来我想使用convert（xx，“ F”，“ C”）将Farenheit转换为Celcius ，我无法获得结果。我认为数据本身存在问题。我将单元格格式化为数字，或者将值复制并粘贴到新列中，但是它们都不起作用。

然后我将data.frame导入R，并尝试使用R进行一些数据格式化。我检查了Temperature列的类别，该列显示“字符”：

class(a$Temperature)
#"character"

a$Temperature <- gsub("F","",a$Temperature)
# this command remmoved "F"

as.numeric(a$Temperature)
#Warning message: NAs introduced by coercion 

as.numeric(unlist(a$Temperature))
#still the same warning message

从excel中，我创建了一个新列，该列从温度中删除了“ F”，并在R中使用此列将“字符”转换为“数字”，但仍然收到警告消息。我不知道该如何处理。有人可以帮我吗？谢谢！

按照下面的建议，我要粘贴输出

dput(head(a))

#structure(list(Time = structure(c(-2209075140,-2209074840,-2209074540,-2209074240,-2209073940,-2209073640),tzone = "UTC",class = c("POSIXct","POSIXt")),Temperature = c("60.0 ","59.9 ","59.8 ","59.7 ","59.6 ","59.5 "),`T(F)` = c("60.0 ",`Dew Point` = c("48.2 F","48.1 F","48.4 F","48.3 F","48.2 F","48.1 F"),Humidity = c("65 %","65 %","66 %","66 %"),Wind = c("WSW","WSW","WSW"),Speed = c("0.0 mph","0.0 mph","0.0 mph"),Gust = c("0.0 mph",Pressure = c("29.88 in","29.88 in","29.88 in"),`Precip. Rate.` = c("0.00 in","0.00 in","0.00 in"),`Precip. Accum.` = c("0.00 in",UV = c(0,0),Solar = c("0 w/m²","0 w/m²","0 w/m²")),row.names = c(NA,-6L),class = c("tbl_df","tbl","data.frame"))

解决方法

如果只想转换“温度”列，则可以考虑以下选项。

数据

df <- structure(list(Time = c("12:04 AM","12:09 AM","12:14 AM","12:19 AM","12:24 AM","12:29 AM"),Temperature = c("69.4 F","69.2 F","68.8 F","68.5 F","68.3 F","68.0 F"),Dew.Point = c("45.9 F","46.0 F","45.8 F","45.7 F","45.7 F"),Humidity = c("43 %","43 %","44 %","45 %"),Wind = c("NE","NE","NE"),Speed = c("0.0 mph","0.0 mph","0.0 mph"),Gust = c("0.0 mph",Pressure = c("29.93 in","29.94 in","29.95 in","29.95 in"),Precip..Rate. = c("0.00 in","0.00 in","0.00 in"),Precip..Accum. = c("0.00 in",UV = c(0L,0L,0L),Solar = c("0 w/m²","0 w/m²","0 w/m²")),class = "data.frame",row.names = c(NA,-6L))

代码

library(dplyr)
library(stringr)
df2 <- df %>% 
  mutate(Temperature2 = as.numeric(str_extract(Temperature,"[\\d\\.]+"))) %>% 
  relocate(Temperature2,.after = Temperature)

df2[,2:3]
#   Temperature Temperature2
# 1      69.4 F         69.4
# 2      69.2 F         69.2
# 3      68.8 F         68.8
# 4      68.5 F         68.5
# 5      68.3 F         68.3
# 6      68.0 F         68.0
str(df2$Temperature2)
# num [1:6] 69.4 69.2 68.8 68.5 68.3 68

,

也许这有帮助。 在此函数中，嵌套了几个不同的函数，例如从字符变量更改为数字。还有gsub，它将逗号更改为空白。您应该只更改逗号以表示正在更改的内容。从未尝试过将其与字母一起使用，但这可能是一种解决方案。这是代码：

data666

应用函数将函数应用于整个数据集。 2表示它逐列执行。如果要逐行更改它，则必须将2更改为1。