Converting geo coordinates from degree to decimal

Question

I want to convert my geographic coordinates from degrees to decimals, my data are as follows:

         lat     long 105252 30°25.264 9°01.331 105253 30°39.237 8°10.811 105255 31°37.760 8°06.040 105258 31°41.190 8°06.557 105259 31°41.229 8°06.622 105260 31°38.891 8°06.281 

I have this code but I can not see why it is does not work:

convert<-function(coord){ tmp1=strsplit(coord,"°") tmp2=strsplit(tmp1[[1]][2],"\\.") dec=c(as.numeric(tmp1[[1]][1]),as.numeric(tmp2[[1]])) return(dec[1]+dec[2]/60+dec[3]/3600)  }  don_convert=don1 for(i in 1:nrow(don1)){don_convert[i,2]=convert(as.character(don1[i,2]));              don_convert[i,3]=convert(as.character(don1[i,3]))} 

The convert function works but the code where I am asking the loop to do the job for me does not work.

Any suggestion is apperciated.

Answer 1

Use the measurements package from CRAN which has a unit conversion function already so you don't need to make your own:

x = read.table(text = "    lat     long 105252 30°25.264 9°01.331 105253 30°39.237 8°10.811 105255 31°37.760 8°06.040 105258 31°41.190 8°06.557 105259 31°41.229 8°06.622 105260 31°38.891 8°06.281", header = TRUE, stringsAsFactors = FALSE) 

Once your data.frame is set up then:

# change the degree symbol to a space x$lat = gsub('°', ' ', x$lat) x$long = gsub('°', ' ', x$long)  # convert from decimal minutes to decimal degrees x$lat = measurements::conv_unit(x$lat, from = 'deg_dec_min', to = 'dec_deg') x$long = measurements::conv_unit(x$long, from = 'deg_dec_min', to = 'dec_deg') 

Resulting in the end product:

                    lat             long 105252 30.4210666666667 9.02218333333333 105253         30.65395 8.18018333333333 105255 31.6293333333333 8.10066666666667 105258          31.6865 8.10928333333333 105259         31.68715 8.11036666666667 105260 31.6481833333333 8.10468333333333 

Answer 2

Try using the char2dms function in the sp library. It has other functions that will additionally do decimal conversion.

library("sp") ?char2dms