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..... )) I do agree that we should strongly consider such a change. Martin -------------- next part -------------- A non-text attachment was scrubbed... Name: factor-excl.diff Type: text/x-diff Size: 637 bytes Desc: not available URL: <https://stat.ethz.ch/pipermail/r-devel/attachments/20160827/b62dd60f/attachment.bin>

In R devel r71157, 'droplevels' documentation, in "Arguments" section, says this about argument 'exclude'. passed to factor(); factor levels which should be excluded from the result even if present. Note that this was implicitly NA in R <= 3.3.1 which did drop NA levels even when present in x, contrary to the documentation. The current default is compatible with x[ ,