Defining polygon object by identifying lines in R - r

Question

I have a dataset contains lines and I have imported them into R. I want to take a close look at the coordinates of them and define the identical first and last coordinate of each point if there is some -->(looking for polygon). Therefore, I am using Slot which makes me able to have a close look at the details of the desired object.
My final goal is to define the number of identical point coordinates(First and last) for each line in order to discover the number of the potential polygon in my data.
recapping my difficulty is the following question:
How many of lines objects have potential to be a polygon?
To do so, I have done several steps:
In the first step, I read my data into R.
The second step, I have used slot to have a close look at the coordinate of each point(Sequence of points represent line object).
the third step: I have tried to define the number of identical points but I have faced with an error says CRDs not found
at the following, you can tack a look at the codes
enter library(maptools)
#Read data directly from National Geophysical Data Center (NGDC) coastline
#extractor.
shorelinedat="http://www.asdar-book.org/RC1/datasets/auckland_mapgen.dat"
#Assign CRS
llCRS <- CRS("+proj=longlat +ellps=WGS84")
#Read data from mapgen into a SpatialLines object.
auck_shore <- MapGen2SL("auckland_mapgen.dat", llCRS)
#Required code to identify the lines.
lns <- slot(auck_shore, "lines")
table(sapply(lns, function(x) length(slot(x, "Lines"))))
Here is the code in which I faced with the error
#identifying the number of identical coordinates
islands_auck <- sapply(lns, function(x) {
+ crds <- slot(slot(x, "Lines")[[1]], "coords")
+ identical(crds[1, ], crds[nrow(crds), ])
+ })
This is the error
Error in +crds <- slot(slot(x, "Lines")[[1]], "coords") :
object 'crds' not found
I would appreciate if anyone can give a hint.

Answer 1

This is just a guess, are those +s actually in your code? If I try to assign to a variable with a + before it (as you do in the code example you posted), I get the same error you got:
+ crds <- 5
Error in +crds <- 5 : object 'crds' not found
When you run a multi-line block of code, R inserts + in the console to show continuing lines, but that's just a visual effect and they are illegal in your actual code.

Answer 2

The problem I had was related to the syntax in the final code which I modified them in below
islands_auck <- sapply(lns, function(x) {
crds <- slot(slot(x, "Lines")[[1]], "coords")
identical(crds[1, ], crds[nrow(crds), ])
})
table(islands_auck)
so the final result will be
islands_auck
FALSE TRUE
16 64
16 lines without equal first and last coordinate (Closed polygon)
64 lines with closed polygon