1.获得基因组的各染色体的长度信息
$ samtools faidx genome.fa
#生成gemome.fa.fai文件第一列为染色体，第二列为对应染色体长度
chr01 44488843 7 44488843 44488844
chr02 38522657 44488858 38522657 38522658
chr03 34302425 83011523 34302425 34302426
chr04 31904921 117313956 31904921 31904922
chr05 31465669 149218885 31465669 31465670
chr06 29481096 180684562 29481096 29481097
chr07 26142479 210165666 26142479 26142480
chr08 23295356 236308153 23295356 23295357
chr09 21309744 259603517 21309744 21309745
chr10 20413421 280913269 20413421 20413422
2.根据染色体的长度产出区域文件：
$ bedtools makewindows -g genome.fa.fai -w 100000 >region.bed
$ head region.bed
chr01 0 100000
chr01 100000 200000
chr01 200000 300000
chr01 300000 400000
chr01 400000 500000
3.输入vcf文件统计不同区域里面变异个数
$ bedtools coverage -a region.bed -b q4.vcf -counts >result.txt
