Insufficient number of observations

[srbehera11]

Can you please suggest what values should be manually assigned for resolving the following error?

[17/10/2017 11:26:33] Sorting splice-graphs by read count [17/10/2017 11:26:33] Finished sorting splice-graphs by read count

[17/10/2017 11:26:33] Spawning 1 thread(s) for fetching alignments and 1 i/o thread [17/10/2017 11:26:33] Estimating fragment length distribution from 4 transcripts longer than 2500 nucleotides ERROR: Insufficient number of observations for estimating the fragment length distribution parameters. Please specify these manually using the --frag-mean and --frag-sd options.