Getting "Error in par(pin = p)" when using spTransform in R

Question

I am trying to apply a projection to the following dataset from the USGS: https://www.sciencebase.gov/catalog/item/581d052be4b08da350d524ce. After reading in the dataset, the "proj4string" slot shows the data has these CRS arguments:

+proj=longlat +datum=NAD83 +no_defs +ellps=GRS80 +towgs84=0,0,0

Here is a simplified piece of code that results in the error in question:

library(rgdal)
library(maps)
Highway_longlat <- readOGR(dsn = "SourceFolder")
Highway_merc <- spTransform(x = Highway_longlat, CRSobj = CRS(projargs = "+proj=merc"))
map(database = Highway_merc)

I get this error:

Error in par(pin = p) : invalid value specified for graphical parameter "pin"

I was not able to find any information on this error that seemed related to my situation.

• Kelvin Singh: The command plot(Highway_merc) produces the expected image with no error so it seems like the error is not coming from spTransform but rather from the map function.

Answer 1

Usually one would define the projection in R, before applying spTransform. Did you try this?

library(sp)
coordinates(highway_longlat) <- ~long+lat #Refers to your Long and Lat columns
proj4string(highway_longlat) <- CRS("+init=epsg:4326") # set it to WGS84
highway_merc <- spTransform(highway_longlat,CRS("+proj=merc")) 
#I usually set it to the EPSG code within the CRS ( ), but the above should work as well

• Kelvin Singh: I gave it a shot but ran into a couple issues. (1) I think the 'coordinates' function is for a SpatialPointsDataFrame whereas my dataset is a SpatialLinesDataFrame. (2) When applying CRS to proj4string, I get a warning that I am overriding the existing CRS. Thanks for your suggestion.
• Vijay Ramesh: You can exclude the coordinates function. It is optional. If you can e-mail your code to vjjan91 at gmail ; happy to take a look.