[BioC] Question about MM > PM

Laurent Gautier laurent at cbs.dtu.dk
Sun Oct 12 21:19:14 MEST 2003

On Sun, Oct 12, 2003 at 03:06:45PM -0400, s0uchi02 wrote:
> Hello.  I have a question about MM > PM.
> In the "Textual descrtion of affy," it is stated that if the following command 
> is used:
> > mean(mm(Dilution) > pm(Dilution))
> [1] 0.2746048
> Is this 0.2746048 % or 27.46048% of the MM are larger than PM?

'mm(Dilution) > pm(Dilution)' returns a vector of booleans ('logical'
in R terminology).
Calling 'mean()' on the results implies a cast to integers (TRUEs
become 1 and FALSEs become 0) then the mean is computed. In other
words, each time MM>PM you have 1, and zero when MM<PM. You sum
all the ones and zeros and divide by length of the vector...
which should bring you to the conclusion that roughly 30% of the MM are larger
the PM.

Hopin' it helps,


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