I need to perform genotype imputation on my data. The build of my data is hg18, so first I want to convert it into hg19. My Plink files are divided by chromosomes. When I use liftOver to lift my coordinates to hg19, I lose chromosomes 13,14,15,21 and 22 since none of the variants within these chromosomes are updated from hg18 to 19 (due to "partially deleted in new", "split in new", etc). How can I deal with this and not lose my data for these chromosomes?