Using time series (two condition with 4 time point) data in DESeq2, i got warning while fitting by GLM ??
bckCDS <- DESeqDataSetFromMatrix(countData = x, colData=ExpDesign, design= ~condition.label + condition.Time + condition.label:condition.Time)
ddsLRT= DESeq (bckCDS, test =LRT, reduced = ~condition.label + condition.Time) estimating size factors estimating dispersions gene-wise dispersion estimates mean-dispersion relationship NOTE: fitType=parametric, but the dispersion trend was not well captured by the function: y = a/x + b, and a local regression fit was automatically substituted. specify fitType=local or mean to avoid this message next time. final dispersion estimates fitting model and testing
May i have fit it by "local", indeed its work by this however, my question is why its not working by "fitType='parametric'". What is advantage and disadvantage of it.