How to show values of long and lat on a map?

I have a file with a projection of EPSG:3410 that I want simply to plot using R. As the projection is in meters, I have a problem with the lat and long values (axes).You can see on the map that instead of 90 -90 180 -180 there are other numbers.

the code to plot this map:

       con1 <- file("C:\\Users\\data.bin","rb")
       r = raster(y)
      extent(r) = extent(c(xmn=-17334194,xmx=17334194,ymn=-7356860,ymx=7310585))
      plot(r)
      plot(wbuf, add=TRUE)

How I can replace those unusual values on the map with 90 -90 180 -180 (so no changes on the original file)
How I can get rid of the space up and bottom of the map?

Solution

Here's some workarounds to avoid the white space and to add the axis labels. Since both maps are in metres, it's not easy to plot lat-lon labels.

library(raster) # for xmin, ymin etc.

# plot raster without axes and box
plot(r, asp=1, axes=F, box=F)

# add polygons
plot(wbuf, add=TRUE, axes=F)

# draw bounding box at raster limits 
rect(xmin(r), ymin(r), xmax(r), ymax(r))

To add lat-lon ticks, we need to convert from the EPSG:3410 (metres) projection to lat-lon (degrees). We can create dummy spatial points in latlon and convert those to 3410, then extract the converted coordinates to add the ticks

# y axis:
x = -180
y = seq(-90,90,30) # you can adapt this sequence if you want more or less labels
S <- SpatialPoints(cbind(x,y), proj4string = CRS("+proj=longlat +datum=WGS84"))
S2<- spTransform(S, CRS(" +proj=cea +lon_0=0 +lat_ts=30 +x_0=0 +y_0=0 +a=6371228 +b=6371228 +no_defs ")) 
axis(side = 2, pos=xmin(r), at = S2@coords[,'y'], lab=y, las=1)


# x axis
y = -90
x = seq(-180,180,30)
S <- SpatialPoints(cbind(x,y), proj4string = CRS("+proj=longlat +datum=WGS84"))
S2<- spTransform(S, CRS(" +proj=cea +lon_0=0 +lat_ts=30 +x_0=0 +y_0=0 +a=6371228 +b=6371228 +no_defs "))
axis(side = 1, pos=ymin(r), at = S2@coords[,'x'], lab=x)

Another option is to reproject the raster, so the maps are lat-lon (degrees):

# reproject and plot raster
r2 = projectRaster(r, crs=CRS("+proj=longlat +datum=WGS84"))
plot(r2, axes=F, box=F)

# there's an option to disable internal boundaries, which is nice
map(database = 'world', regions = '', interior = F, add=T)

# still have to add bounding box and axes
rect(xmin(r), ymin(r), xmax(r), ymax(r))
axis(1, pos = ymin(r2))
axis(2, pos= xmin(r2), las=1)