I am using the Tutorials for the R/Bioconductor package SNPRelate trying to run a relatedness analysis. I have a VCF output file from STACKS for mangrove (Avicennia germinans) populations. The VCF includes the following information:

INFO ID=NS,Number=1,Type=Integer,Description="Number of Samples With Data" INFO ID=AF,Number=.,Type=Float,Description="Allele Frequency" FORMAT ID=GT,Number=1,Type=String,Description="Genotype" FORMAT ID=DP,Number=1,Type=Integer,Description="Read Depth" FORMAT ID=AD,Number=1,Type=Integer,Description="Allele Depth" FORMAT ID=GL,Number=.,Type=Float,Description="Genotype Likelihood" INFO ID=locori,Number=1,Type=Character,Description="Orientation the corresponding Stacks locus aligns in"

The first two rows of the VCF file has:

CHROM POS ID REF ALT QUAL FILTER INFO FORMAT BC-B39.all BC102.all ............. un 1105 16_53 A G . PASS NS=2;AF=0.500;locori=p GT:DP:AD ./.:0:.,. ./.:0:.,. ..............

I am running the code based on the tutorial and have run the following code:

setwd("~/Desktop")
vcf_test1 <- read.vcf("/Users/allisavincent/Desktop/Full_Study_Current.vcf")
vcf.fn <- "/Users/allisavincent/Desktop/Full_Study_Current.vcf"
seqarray_test2 <- snpgdsVCF2GDS(vcf.fn, "Full_Study.gds")
snpgdsSummary("/Users/allisavincent/Desktop/Full_Study.gds")
genofile <- snpgdsOpen("/Users/allisavincent/Desktop/Full_Study.gds")
pop_code <- scan("/Users/allisavincent/Desktop/pop.txt", what=character())
set.seed(100)
snp.id <- samplesnpset.id, 1500)  # random 1500 SNPs
    Error in samplesnpset.id, 1500) : object 'snpset.id' not found
ibd <- snpgdsIBDMLE(genofile, sample.id=YRI.id, snp.id=snp.id,
+                     maf=0.05, missing.rate=0.05, num.thread=2)
Error in stopifnotis.nullsample.id) | is.vectorsample.id) | is.factorsample.id)) : 
  object 'YRI.id' not found

When the GDS file is created, snpgdsVCF2GDS automatically generates a unique integer ID for each variant. This is what you would use to identify variants in SNPRelate functions.

snp.id <- read.gdsn(index.gdsn(genofile, "snp.id"))
sample.id <- read.gdsn(index.gdsn(genofile, "sample.id"))

Your code has several errors that are not related to the contents of the VCF file: you have not defined the objects snpset.id or YRI.id.