Question

The following data frame represents latitude and longitude decimal coordinates. I wish to using + and – to show whether the decimal degrees are North, South, East or West (in the latitude and longitude column).

So, latitude would be positive if the decimal degrees were N.
… the latitude would be negative if the decimal degrees were S.
… the longitude would be positive if the decimal degrees were E
and the longitude would be negative if the decimal degrees were W.

a <- c(1:3)
Lat <- c(54.5, 55.2, 10.1)
NS <- c("N","N","S")
Long <- c(1.2, 0.5, 1.3)
EW <- c("W","E","W")
df1 <- data.frame(a,Lat,NS,Long,EW)

How would I do this in R? Any advice would be much appreciated.

Answer 1

Use ifelse:

df1 <- within(df1, {
             Lat <- ifelse(NS=="N", Lat, -Lat)
             Long <- ifelse(EW=="E", Long, -Long)
})

df1
  a   Lat NS Long EW
1 1  54.5  N -1.2  W
2 2  55.2  N  0.5  E
3 3 -10.1  S -1.3  W

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I use within() to reduce the amount of typing.