R数据框根据其他数据框填充缺失值

Question

我有一个大型数据集，其中每个站点都有相同的纬度和经度。在数据集中，某些行缺少纬度和经度，而是显示“未知”。我需要用其他数据不丢失的站点的经纬度来填充未知数。

在此示例中，我希望第 5 行插入 3 和 8 作为纬度和经度:

> station <- c("a","b","c","c","c")
> lat <- c("1","2","3","3","unknown")
> lon <- c("6","7","8","8","unknown")
> data.frame(station,lat,lon)
  station     lat     lon
1       a       1       6
2       b       2       7
3       c       3       8
4       c       3       8
5       c unknown unknown

我的数据集中有一百万行，如果需要几分钟才能完成也没关系，因为它在分析开始之前只运行一次。除非确实有必要，否则我宁愿不安装另一个软件包。

Answer 1

也许是这样的 -

df$station <- as.character(df$station)

unknownstations <- unique(subset(df,df$lat == "unknown","station"))
unknownstationscoords <- unique(subset(df,station %in% unknownstations$station & lat != "unknown"))

for( i in unknownstations$station)
{
df[df$station == i,"lat"] <- subset(unknownstationscoords,station %in% i,"lat")
df[df$station == i,"lon"] <- subset(unknownstationscoords,station %in% i,"lon")
}