Dear all,

I want to combine the packages minfi and wateRmelon to analyse my EPIC methylation data. I loaded my data as an RGChannelSetExtended into R with Minfi. Next I wanted to filter out low quality samples and probes with the pfilter function of wateRmelon. Downside: the function returns a Methylset, which I cannot use in the preprocessNoob function of Minfi (it requires a RGChannelSet). In the older versions of watermelon I noticed it was possible to return a RGChannelSetExtended.

Is there anyone who can help me with this problem?

Best,

Sara

Hi Sara,

Performing pfilter of RGChannelSets has always been problem due to how the detection p values are calculated for the probes are calculated. The previous method did return an RGChannelSet which then required the manual filtering of data after normalization but this has been changed for a while now.

If you do want to use pfilter the only thing I can recommend is to run pfilter on your data and store it to an object, then normalize the older data object with preprocessNoob then subset the normalised data by the row and colnames of the pfilter object.

filt <- pfilter(data)
norm <- preprocessNoob(data)
norm_filt <- norm[rownames(filt), colnames(filt)]

I know it is not the most ideal method as we do recommend that you apply pfilter prior to normalization. We will look into this and try and come up with something for the upcoming bioconductor version.