无法在R中将字符转换为数字

Question

我从以下网站“weather underground”复制并粘贴了天气信息进行一些数据分析，数据如下所示：

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

如你所见，温度等信息都有文字，无法计算。在 excel 中，我使用 substitute(xx,"F","") 从“温度”列中删除 F，但随后我想使用 convert(xx,"F", “C”），我无法得到结果。我认为数据本身有问题。我将单元格格式化为数字或将值复制并粘贴到新列，但都没有用。

然后我将 data.frame 导入 R 并尝试使用 R 进行一些数据格式化。我检查了温度列的 class，它显示“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，我创建了从温度中删除“F”的新列，并在 R 中使用它来将“字符”转换为“数字”，我仍然收到警告消息。我不知道如何处理这个问题。有人可以帮我解决这个问题吗？谢谢！

按照下面的建议，我粘贴来自

的输出

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 ", "59.9 ", "59.8 ", "59.7 ", 
"59.6 ", "59.5 "), `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 %", "66 %", "66 %"), Wind = c("WSW", "WSW", "WSW", "WSW", 
"WSW", "WSW"), Speed = c("0.0 mph", "0.0 mph", "0.0 mph", "0.0 mph", 
"0.0 mph", "0.0 mph"), Gust = c("0.0 mph", "0.0 mph", "0.0 mph", 
"0.0 mph", "0.0 mph", "0.0 mph"), Pressure = c("29.88 in", "29.88 in", 
"29.88 in", "29.88 in", "29.88 in", "29.88 in"), `Precip. Rate.` = c("0.00 in", 
"0.00 in", "0.00 in", "0.00 in", "0.00 in", "0.00 in"), `Precip. Accum.` = c("0.00 in", 
"0.00 in", "0.00 in", "0.00 in", "0.00 in", "0.00 in"), UV = c(0, 
0, 0, 0, 0, 0), Solar = c("0 w/m²", "0 w/m²", "0 w/m²", "0 w/m²", 
"0 w/m²", "0 w/m²")), row.names = c(NA, -6L), class = c("tbl_df", 
"tbl", "data.frame"))

Answer 1

如果您只想转换温度列，您可以考虑以下选项。

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", "45.7 F"), Humidity = c("43 %", 
"43 %", "44 %", "44 %", "44 %", "45 %"), Wind = c("NE", "NE", 
"NE", "NE", "NE", "NE"), Speed = c("0.0 mph", "0.0 mph", "0.0 mph", 
"0.0 mph", "0.0 mph", "0.0 mph"), Gust = c("0.0 mph", "0.0 mph", 
"0.0 mph", "0.0 mph", "0.0 mph", "0.0 mph"), Pressure = c("29.93 in", 
"29.94 in", "29.94 in", "29.95 in", "29.95 in", "29.95 in"), 
    Precip..Rate. = c("0.00 in", "0.00 in", "0.00 in", "0.00 in", 
    "0.00 in", "0.00 in"), Precip..Accum. = c("0.00 in", "0.00 in", 
    "0.00 in", "0.00 in", "0.00 in", "0.00 in"), UV = c(0L, 0L, 
    0L, 0L, 0L, 0L), Solar = c("0 w/m²", "0 w/m²", "0 w/m²", 
    "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

Answer 2

也许这个，有帮助。在这个函数中嵌套了几个不同的函数，例如从字符变量变为数字变量。还有 gsub，它将逗号更改为空 space。您应该只将逗号更改为字母您正在更改的内容。从未尝试过它是否适用于字母，但这可能是一种解决方案。这是代码：

data666 <- apply(data, 2, function(x) as.numeric(as.character(gsub(",", "", x))))

Apply function 对整个数据集应用函数。 2 表示它逐列执行。如果您想逐行更改它，则必须将 2 更改为 1。

无法在R中将字符转换为数字

cannot convert character into numeric in R

excel

r

numeric

character

dataformat