老师，我在执行指令时
Rscript $scriptdir/var_density.R -i snp.unknown_multianno.vcf -b 1000000 -c "darkgreen,yellow,red" -t "SNP Density"
Rscript $scriptdir/var_density.R -i indel.unknown_multianno.vcf -b 1000000 -c "darkgreen,yellow,red" -t "INDEL Density"
无法生成图例，而且只生成了pdf文件，没有jpg文件，报错提示如下：--> Q&A for bioinformatics, please visit the website: https://www.omicsclass.com/
--> R beginners ? I suggest your learning R language: https://study.omicsclass.com/index
SNP-Density Plotting.
Error in seq.default(0, chorm.maxlen/bp, round(xticks[2])) :
invalid '(to - from)/by'
Calls: CMplot -> DensityPlot -> seq -> seq.default
Execution halted，我的参考基因组是scaffold，最长的是1267525bp,最短的是1900bp,共66条，请问这里该怎么解决呢？