Hello all,

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?

Thanks
<p>Depending on the version you are using, this used to be a warning but is now just a message/note.</p>

<p>The printed message here is literally all you need to know. The software cannot find parameters a and b to fit the dispersion over mean trend using that formula (read the manuscript for more information about the point of modeling dispersion over mean).</p>

<p>So a local regression was automatically substituted. There is no further action required by the user.</p>
