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Topic: Peak Data Insertion Problems-Please Try Lowering ppm Param (Read 3016 times) previous topic - next topic

Peak Data Insertion Problems-Please Try Lowering ppm Param

Hello,

When I process my XCMS data for metaXCMS on the R platform I receive this message during feature detection "Peak Data Insertion Problems-Please Try Lowering ppm parameter".  While the process completes and I can move on to the next step, I am wondering what this means and if there is a way I can lower the ppm parameter that is currently set at 25 ppm.

Thank you,
Stacy

Re: Peak Data Insertion Problems-Please Try Lowering ppm Par

Reply #1
Hi Stacy,

the centWave algorithm has a two step feature detection framework.
The first step is the detection of connected centroids, which are called ROI (region of interest).
If within one scan the selection of a centroid is not distinct,
this could be caused by a too large search window (ppm parameter).

If you have not many warnings, you can safely ignore them.
If not, then you should lower your ppm parameter.

Carsten