Question about ROH analysis by Plink 1.9

Hi all,

I have recently tried to estimate runs of homozygosity (ROH) from my vcf file by using plink 1.9.

I ran following code to generate binary files that plink required:

plink --vcf myfile.vcf --make-bed --out out_name --no-sex --no-parents --no-fid --no-pheno --allow-extra-chr

This vcf file only contains one individual and about 3 million SNPs.

I used –allow-extra-chr here because I mapped my sequences to a drift genome.

Then, I used following code (with default parameters), trying to estimate ROH of my sample:

plink -bfile out_name --homozyg --allow-extra-chr

The result gave me 0 ROH, and only header produced in .hom file.

I also tried different parameters with different SNP windows and criterions, such like:

plink -bfile out_name --homozyg --homozyg-window-snp 50 --homozyg-snp 50 --homozyg-window-missing 3 --homozyg-kb 100 --homozyg-density 1000 --allow-extra-chr

However, all the results were the same, that showed :

PLINK v1.90b6.12 64-bit (28 Oct 2019)
(C) 2005-2019 Shaun Purcell, Christopher Chang   GNU General Public License v3
Logging to plink.log.
Options in effect:

  --bfile out_name
  --homozyg-density 1000
  --homozyg-kb 100
  --homozyg-snp 50
  --homozyg-window-missing 3
  --homozyg-window-snp 50

515905 MB RAM detected; reserving 257952 MB for main workspace.
3708761 variants loaded from .bim file.
1 person (0 males, 0 females, 1 ambiguous) loaded from .fam.
Ambiguous sex ID written to plink.nosex .
Using 1 thread (no multithreaded calculations invoked).
Before main variant filters, 1 founder and 0 nonfounders present.
Calculating allele frequencies... done.
3708761 variants and 1 person pass filters and QC.
Note: No phenotypes present.
--homozyg: Scan complete, found 0 ROH.

Results saved to plink.hom + plink.hom.indiv + plink.hom.summary .

Does anyone have idea why this happened to my files?

Will be grateful for any suggestions.

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