Re: NA's
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rgentleman ★ 5.5k
@rgentleman-7725
Last seen 9.6 years ago
United States
And please, let's move these to bioconductor, they are of general interest rather than specific to the management of the project On Wed, Mar 27, 2002 at 12:22:39PM -0800, Anthony Rossini wrote: > Raf - it might be worth documenting your opinions on the matter, to start thinking of how the various approaches compare under different situations. Or is there already a paper on the topic? (I'm sure in the substantive literature, but as to quality...?). > > best, > -tony > > --- > A.J. Rossini Rsrch Asst Professor of Biostatistics > rossini@u.washington.edu http://software.biostat.washington.edu/ > Biostatistics/Univ. of Washington 206-543-1044 (3286=fax) (Thursdays) > HIV Vaccine Trials Network/FHCRC 206-667-7025 (4812=fax) (M/Tu/W) > (Friday location is generally unknown). > > > On Wed, 27 Mar 2002, Rafael A. Irizarry wrote: > > > i have many.. but too complicated for email. call me if you want. a simple > > one (that i dont like much) is to use a hybrid log. checkout hlog in > > madman/Rpacks/affy/R/hlog.R > > > > On Wed, 27 Mar 2002, Yee Hwa Yang wrote: > > > > > Hi All, > > > > > > Sandrine and I are working on some cDNA data where we find there are lot's > > > of negative values which in turn produce NA's after log transform. These > > > negative values arise because foreground intensities are smaller than the > > > background intensities (from image analysis output). > > > > > > For sma, we had created a series of functions log.na, sum.na, mean.na, > > > ...) to handle NA values. For example, we have > > > > > > log.na > > > function (x, ...) > > > { > > > log(ifelse(x > 0, x, NA), ...) > > > } > > > > > > Does anyone have any suggestions about dealing with NA issues in > > > general for cDNA array data? > > > > > > Thank you, > > > Jean & Sandrine > > > > > > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > Jean Yee Hwa Yang > > > Department of Statistics, 367 Evans Hall > > > University of California, Berkeley, CA 94720 > > > Email: yeehwa@stat.berkeley.edu > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > > > > > > > _______________________________________________ > > > Biocore mailing list > > > Biocore@stat.math.ethz.ch > > > http://www.stat.math.ethz.ch/mailman/listinfo/biocore > > > > > > > _______________________________________________ > > Biocore mailing list > > Biocore@stat.math.ethz.ch > > http://www.stat.math.ethz.ch/mailman/listinfo/biocore > > > > > _______________________________________________ > Biocore mailing list > Biocore@stat.math.ethz.ch > http://www.stat.math.ethz.ch/mailman/listinfo/biocore -- +--------------------------------------------------------------------- ------+ | Robert Gentleman phone : (617) 632-5250 | | Associate Professor fax: (617) 632-2444 | | Department of Biostatistics office: M1B28 | Harvard School of Public Health email: rgentlem@jimmy.dfci.harvard.edu | +--------------------------------------------------------------------- ------+
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rgentleman ★ 5.5k
@rgentleman-7725
Last seen 9.6 years ago
United States
On Thu, Mar 28, 2002 at 11:41:28AM +1100, Gordon Smyth wrote: > Dear Jean and Sandrine, > > I've never liked the idea of setting log-ratios to NA when one of the > foregrounds is less than the corresponding background, because this throws > away the information that that channel is very low for that spot. > > One long-term solution would be to treat such values as left censored, > i.e., to mark them as being "below threshold of measurement". All > subsequent analysis of the values would have to accept a censored data format. > > A shorter term solution would be to subtract only a fraction of the > background estimates, to keep the background corrected measurements all > positive. I am hoping to get a chance to look into ways of doing this > without being too ad hoc. > > I haven't seen anything useful in the literature on this topic yet. > > Best wishes > Gordon Those are good points (I've moved this to bioconductor as well). I believe that one might want to do that with values that are positive in some cases as well. For example with oligo arrays (and I expect cDNA) most people don't seem to believe that low values are reliable, hence the left censoring (or Windsorising) point could be set to 20, or 50 (notice that there are no units attached). One of the main problems with this approach is that the analytic tools used to filter genes/ESTs must then account for the censoring and I believe that there are few such devices around. However, I agree that this may be a more attractive solution in the long term. r > > At 12:02 PM 27/03/2002 -0800, Yee Hwa Yang wrote: > >Hi All, > > > >Sandrine and I are working on some cDNA data where we find there are lot's > >of negative values which in turn produce NA's after log transform. These > >negative values arise because foreground intensities are smaller than the > >background intensities (from image analysis output). > > > >For sma, we had created a series of functions log.na, sum.na, mean.na, > >...) to handle NA values. For example, we have > > > > log.na > >function (x, ...) > >{ > > log(ifelse(x > 0, x, NA), ...) > >} > > > >Does anyone have any suggestions about dealing with NA issues in > >general for cDNA array data? > > > >Thank you, > >Jean & Sandrine > > -------------------------------------------------------------------- ------------------- > Dr Gordon K Smyth, Senior Research Scientist, Bioinformatics, > Walter and Eliza Hall Institute of Medical Research, > Post Office, Royal Melbourne Hospital, Vic 3050 > Tel: (03) 9345 2326, Fax (03) 9347 0852, > Email: smyth@wehi.edu.au, www: http://www.statsci.org > > _______________________________________________ > Biocore mailing list > Biocore@stat.math.ethz.ch > http://www.stat.math.ethz.ch/mailman/listinfo/biocore -- +--------------------------------------------------------------------- ------+ | Robert Gentleman phone : (617) 632-5250 | | Associate Professor fax: (617) 632-2444 | | Department of Biostatistics office: M1B28 | Harvard School of Public Health email: rgentlem@jimmy.dfci.harvard.edu | +--------------------------------------------------------------------- ------+
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@laurent-gautier-9
Last seen 10.2 years ago
The use of something like the 'na.action' mentioned before now would let us (or others) plug-in easily their way to treat the NA's.. what about something like log.na <- function(x, na.action=<eventually put="" a="" default="" action="" here="">) { x <- na.action(x) log(x) } note: the handling of negative intensity values could be of general interest... would it make sense to have the collection of function suggested by Yee and Sandrine in a specific package (or in Biobase) ? L. -------------------------------------------------------------- Laurent Gautier CBS, Building 208, DTU PhD. Student D-2800 Lyngby,Denmark tel: +45 45 25 24 85 http://www.cbs.dtu.dk/laurent ~ On Wed, Mar 27, 2002 at 12:02:53PM -0800, Yee Hwa Yang wrote: > Hi All, > > Sandrine and I are working on some cDNA data where we find there are lot's > of negative values which in turn produce NA's after log transform. These > negative values arise because foreground intensities are smaller than the > background intensities (from image analysis output). > > For sma, we had created a series of functions log.na, sum.na, mean.na, > ...) to handle NA values. For example, we have > > log.na > function (x, ...) > { > log(ifelse(x > 0, x, NA), ...) > } > > Does anyone have any suggestions about dealing with NA issues in > general for cDNA array data? > > Thank you, > Jean & Sandrine > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Jean Yee Hwa Yang > Department of Statistics, 367 Evans Hall > University of California, Berkeley, CA 94720 > Email: yeehwa@stat.berkeley.edu > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > _______________________________________________ > Biocore mailing list > Biocore@stat.math.ethz.ch > http://www.stat.math.ethz.ch/mailman/listinfo/biocore -- -------------------------------------------------------------- other email: lgautier@altern.org -------------------------------------------------------------- Laurent Gautier CBS, Building 208, DTU PhD. Student D-2800 Lyngby,Denmark tel: +45 45 25 24 85 http://www.cbs.dtu.dk/laurent ----- End forwarded message ----- -- -------------------------------------------------------------- other email: lgautier@altern.org -------------------------------------------------------------- Laurent Gautier CBS, Building 208, DTU PhD. Student D-2800 Lyngby,Denmark tel: +45 45 25 24 85 http://www.cbs.dtu.dk/laurent
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