How to Convert data frame to spatial coordinates

Question

I have been working on earthquake data that has lat long values, and I want to convert those lat long values to spatial coordinates.

Suppose I have the following data set df:

longitude          latitude         128.6979    -7.4197         153.0046    -4.7089         104.3261    -6.7541         124.9019    4.7817         126.7328    2.1643         153.2439    -5.6500         142.8673    23.3882         152.6890    -5.5710 

I want to convert it into spatial points. Something like this:

 lon        lat   [1,] 2579408.24 1079721.15 [2,] 2579333.69 1079729.18 [3,] 2579263.65 1079770.55 [4,] 2579928.04 1080028.46 [5,] 2579763.65 1079868.92 [6,] 2579698.00 1079767.97 

I used the following code:

library(sp) df.sp<-df coordinates(df.sp)<-~x+y 

But I receive the following error:

Error in `[.data.frame`(object, , -coord.numbers, drop = FALSE) :    undefined columns selected 

Answer 1

First, you take the columns of lon and lat and create an object for coord. Then, you subtract them from the original data frame and create a new object. You finally use SpatialPointsDataFrame() to create a SpatialPointsDataFrame. When you create a SpatialPointsDataFrame, you need to assign proj4string. Choose an appropriate one for you.

In your case, you do not have any other columns but lon and lat, the method won't work. I purposely left lon and lat @data.

DATA

mydf <- structure(list(longitude = c(128.6979, 153.0046, 104.3261, 124.9019,  126.7328, 153.2439, 142.8673, 152.689), latitude = c(-7.4197,  -4.7089, -6.7541, 4.7817, 2.1643, -5.65, 23.3882, -5.571)), .Names = c("longitude",  "latitude"), class = "data.frame", row.names = c(NA, -8L))   ### Get long and lat from your data.frame. Make sure that the order is in lon/lat.  xy <- mydf[,c(1,2)]  spdf <- SpatialPointsDataFrame(coords = xy, data = mydf,                                proj4string = CRS("+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0"))   #> str(spdf) #Formal class 'SpatialPointsDataFrame' [package "sp"] with 5 slots #..@ data       :'data.frame':  8 obs. of  2 variables: #.. ..$ longitude: num [1:8] 129 153 104 125 127 ... #.. ..$ latitude : num [1:8] -7.42 -4.71 -6.75 4.78 2.16 ... #..@ coords.nrs : num(0)  #..@ coords     : num [1:8, 1:2] 129 153 104 125 127 ... #.. ..- attr(*, "dimnames")=List of 2 #.. .. ..$ : NULL #.. .. ..$ : chr [1:2] "longitude" "latitude" #..@ bbox       : num [1:2, 1:2] 104.33 -7.42 153.24 23.39 #.. ..- attr(*, "dimnames")=List of 2 #.. .. ..$ : chr [1:2] "longitude" "latitude" #.. .. ..$ : chr [1:2] "min" "max" #..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slot #.. .. ..@ projargs: chr "+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0" 

Answer 2

Or using sf instead of sp objects (check out more about Simple Features for R or migrating from sp to sf here):

library(sf)  # the given data above my.df <- read.table(text="                     longitude    latitude                     128.6979    -7.4197                     153.0046    -4.7089                     104.3261    -6.7541                     124.9019    4.7817                     126.7328    2.1643                     153.2439    -5.6500                     142.8673    23.3882                     152.6890    -5.5710",                     header=TRUE)  # Convert data frame to sf object my.sf.point <- st_as_sf(x = my.df,                          coords = c("longitude", "latitude"),                         crs = "+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0")  # simple plot plot(my.sf.point)  # interactive map: library(mapview) mapview(my.sf.point)  # convert to sp object if needed my.sp.point <- as(my.sf.point, "Spatial")