I aligned Illumina fastq reads (2x100bp) to transcriptome using Bowtie2 and found that the mean insert size is ~180bp and SD ~60bp. By plotting the insert sizes I found that the data is right skewed and the skewness is ~1.69 which was obtained using "skewness" from the package "e1071".
I tried to obtain this type of data from
rsnorm where we can specify skewness parameter.
rsnorm(3000000, mean = 180, sd = 60, xi = 1.69)
xi is the skewness parameter.
But the plot I get is more symmetrical and also skewness is 0.69 while the mean and SD remain the same (180bp and 60bp respectively).
I tried with different values for Xi and I always end up with values -1 to 1. So I am confused here.
It will be helpful to know where I am going wrong.
Thanks in advance