从R中的文本中分离日期

Question

我有一个字符串向量，其中包含站点中收集的变量的开始和结束日期的重复模式。 这是第一个条目：

“ 1942-10-06,1996-03-31雪深（in / mm）1942-11-01,1996-03-31降雪（in / mm）1942-10-01,1997-12-27生长度日加热度日平均温度（F / C）最高温度（F / C）1950-08-01,1970-03-31观测时间温度（F / C）1942-10-01,1997-12-27最低温度（F / C）1942-10 -01,1996-03-31降水（in / mm）“

有人可以帮我将每个字符串重新格式化为包含开始日期，结束日期和变量名称的表吗？

Answer 1

以下代码应遵循有关数据格式化方式的一些假设：

1. 您的开始日期为“ yyyy-mm-dd”或“ yyyy-dd-mm”格式，后跟逗号，
2. 您的结束日期与开始日期的格式相同，并以逗号结尾，并且
3. 您的变量名在结束日期之后，不包含数字。

正如Oriol Mirosa所暗示的，这些假设可能不成立。

# Your string
string = "1942-10-06,1996-03-31Snow Depth (in/mm)1942-11-01,1996-03-31Snowfall (in/mm)1942-10-01,1997-12-27Growing Degree DaysHeating Degree DaysAverage Temperature (F/C)Maximum Temperature (F/C)1950-08-01,1970-03-31Observation Time Temperature (F/C)1942-10-01,1997-12-27Minimum Temperature (F/C)1942-10-01,1996-03-31Precipitation (in/mm)"

# Extract text matching Assumptions 1-3, respectively, above
library(stringr) 
start_dates = str_extract_all(string, "[0-9]{4}-[0-9]{2}-[0-9]{2},")
end_dates = str_extract_all(string, ",[0-9]{4}-[0-9]{2}-[0-9]{2}")
var_names = str_extract_all(string, 
                           ",[0-9]{4}-[0-9]{2}-[0-9]{2}([^[0-9]])+")

# Remove the irrelevant bits (e.g., leading/trailing commas)
start_dates = as.Date(gsub(",", "", unlist(start_dates))) #remove ","
end_dates = as.Date(gsub(",", "", unlist(end_dates))) #remove ","
var_names = gsub(",[0-9]{4}-[0-9]{2}-[0-9]{2}", "", unlist(var_names))

# Put into table
X = data.frame("Start_date" = start_dates, 
               "End_date" = end_dates,
               "Var_name" = var_names)