Thanks for the syntax. But, please specify version of PLINK used for conversion and merging. I am working on exome VCF files from IonProton. Converted VCFs using PLINK1.9 to PED/MAP files. But when I try to merge the file-set (PED/MAP) using PLINK1.9 it gives error about multiallelic SNPs. I already removed multiallelic records from VCF files using bcftools
bcftools view -m2 -M2 -v snps input.vcf
Still it gives the same error. Any further help on this Many thanks