[Bioc-devel] BioC 2.5: Added scanDates slot to Biobase's eSetclass

I believe that [1] this is not phenoData and [2] it is critical to
understanding the data set.

The second point says that there should definitively be some place to
store it; the first point suggests that the phenoData slot is not
ideal. ?One strong argument against including it in the phenoData slot
comes from the situation when replicate assays are performed on the same
sample. The phenotypic/clinical/demographic data for repeated samples is
the same, but the experimental characteristics (run date, etc) can be
very different. And, as already pointed out by several people, there are
numerous other experimental characteristics (such as sample preparation
date) that could also affect the interpretation of the results.

So, I would argue in favor of a new slot (probably implemented as yet
another AnnotatedDataFrame) called something like
experimentCharacteristics, in which scanDate would be one commonly used
column.

? ?Kevin

James MacDonald wrote:

If by phenoData we want to mean 'Any random information that may or may not be phenotypic in nature', then scan date should certainly go there. However, it seems to me that up to this time we have been very careful about what goes where precisely because we didn't want to stuff random information in odd places.

To me, the idea of having different slots with names like phenoData and assayData and featureData implies to the end user what sort of data are in there.

If we are to store non-phenotypic, non-biological data somewhere, I think it makes sense to have another slot. All the slots we have in the eSet class right now are for data that are conceptually quite different from things like 'who ran these chips' or 'what day they were run' or whatever. So putting this sort of data in with phenotypic data makes no sense to me at all.

Jim

Kasper Daniel Hansen <khansen at stat.berkeley.edu> wrote:

I am adding my support to Laurent: I think scanDate is simply another
column in the phenotype info, indeed something I always put in, if I
have it available (well, actually I am usually more interested in prep
date). Putting in a new slot seems counter intuitive to me.

Kasper

On Jun 18, 2009, at 12:07 , Patrick Aboyoun wrote:

Laurent,
The scan dates were singled out originally because we have
encountered data sets at the Hutch that appear to have a scan date
effect and wanted a location to store this information so it can be
included in the analysis. As you mentioned, there are other
variables that could be important as well and shouldn't be ignored.

Given that you have been actively working towards a solution of
managing array metadata, you can help create a design that can be
implemented in the Biobase package. Martin Morgan is currently
leading this effort and we can start a dialog off-list (so as not to
spam the rest of the developers with minutiae) with those who are
interested to hammer out a solution to this problem. I think once
the requirements are formally expressed, we can easily put together
a design that meets the user's needs.


Patrick



Laurent Gautier wrote:

Patrick,

The conceptual distinction you want to make can be seen as
artificial.

When you start introducing "arrayData" as a separated entity, you
will soon have to introduce "samplepreparationData" (what
extraction protocol was used, where there any biopsy, etc...),
"imageAnalysisData" (you know grid alignment, spot segmentation).
Is it reasonable to add a slot each time ? Moreover, those
categories can probably also be broken down into subcategories.
Finally, what is making the scanning date so important ?
Wouldn't the version of the software used, or the scanner, or the
scanner settings, or the name of the person who performed the
scanning be of relevance ?

One route would be to construct an initial AnnotatedDataFrame and
populate it with whatever you fancy from the raw-data files (scan
date, software, etc...). I have been going way with my homebrew
infrastructure, and it has so far been leading to quite much
expressivity. Reserved words are not necessarily very limiting (if
sufficiently specific, say "array_scan_date" and the associated
varMetaData = "Date when scanning the hybridized microarray"), and
I'd think better to carefully design and document what is happening
when one is trying to add an other column with the same name rather
than rely on security-through-obscurity with mangled names.



L.





Patrick Aboyoun wrote:

Laurent,
As you mentioned the existing phenoData infrastructure could be
used to house information like scan dates, scanner model, and
scanning software version, but this information is not
conceptually phenotype data and, and adding it to an
AnnotatedDataFrame comes with the limitation of using reserved
words (maybe name mangled like .__ScanDates__?) for column names
in the AnnotatedDataFrame.

The internal discussion we have been having to making this more
general is to add a different slot (candidate name arrayData) to
eSet (and removing the scanDates slot) that would house the type
of information we have been discussing in a combination of
dedicated slots like scanDates and a catch all AnnotatedDataFrame
slot for less universal data. This design would separate the array
data from the phenotype data and having dedicating slots for
important information like scan dates would avoid having to manage
special columns in an AnnotatedDataFrame.

As you rightly point out we need to ensure we support a rich suite
of functionality like "[", subset, etc., but this can all be
handled through methods for the eSet class.

Keep in mind that this recent change is just a first step, not a
final design, and with your help and input from the rest of the
BioC developer community, we can ensure we end up with a
sufficiently useful microarray data infrastructure.

Cheers,
Patrick


Quoting Laurent Gautier <laurent at cbs.dtu.dk>:

Patrick,

There are indeed always several ways to address needs, and my
comment
is mostly pointing at the fact that creating yet-an-other slot is
not
necessary since one can currently store such data into phenoData
(into
a column named... say "scan_date").

I would in fact qualify of overbuilding the approach that adds a
new
(and exclusive) slot while improving the exiting infrastructure
could
perfectly answer the needs. So today it's "scanDates", and next
could
be "scannerModel", or "scanningSoftwareVersion".

I have been a little unclear (even to myself) in my comment about
using
"[", so here are more details. *If* the extract operator was made
to
evaluate expressions such as the function subset() does, or in
fact if
a method subset was implemented for eSet objects, storing all
information into phenoData makes such things nice:

# silly example: only get the control data scanned in the future:
eset[, scan_date > date() & treatment == "control"]
# same with subset:
subset(eset, , scan_date > date() & treatment == "control")

# a little longer to write
eset[, scanDates(eset) > date() & pData(eset) == "control"]


If for some reasons a distinction between phenoData and
like-phenoData-but-can't-be-the-same is needed, please do
consider the
creation of an AnnotatedDataFrame that contains all of them.



L.





Patrick Aboyoun wrote:

Laurent,
We had some immediate need for scan date information and rather
than overbuild a system for managing metadata that we may or
may ?not need, we opted to start simply and then build up as
appropriate. There has been some internal discussions about
managing other metadata along with scan dates, but nothing else
has ?bubbled to the top yet. Your thoughts and design can help
speed up ?this process. The class versioning system in Biobase
supports ?iterative development and we can make further changes
once we lock ?a design in place. One editorial comment I have is
that lots of ?designs are possible for a given need and, for
example, the current ?class properly subsets the scanDates
information using "[" despite ?not being stored in the phenoData
(AnnotatedDataFrame) slot.


Cheers,
Patrick


Quoting Laurent Gautier <laurent at cbs.dtu.dk>:

Hi Patrick,

Storing the scan dates is indeed useful information, and is it
nice to
have it offered at the parsing stage.
However, first comment would be "does it justify a new slot" to
eSet ?

I have been storing scan dates for quite some time now, but
opted for
having them in the phenoData as it made more sense to me, both
on an
implementation standpoint and on practical standpoint (as
standard
extraction of an eset-subset on columns with the "[" operator
works).

If having something specific for scan dates is really really
wished,
would it make make sense to have that by extending
AnnotatedDataFrame ?

In my opinion, the stage at which the the data are extracted
(in that
case when parsing the files coming out of the image analysis)
should
not dictate where the data are stored.
In fact, it might make it for a nice(r) workflow if the function
reading raw array data could return an eSet-inheriting instance
and a
phenoData with information such as dates and file names. I am
working
on a workflow that is in fact getting much more data from the
header (I
suppose that I'd contribute it when enough time to wrap it up).


Just few thoughts,



L.





Patrick Aboyoun wrote:

Dear Bioconductor developers,
The Biocore group has just committed a change to the BioC 2.5
code ?line (Biobase version 2.5.3) to support the use of
microarray scan ?date in statistical analyses by adding a
scanDates slot to ?Biobase's eSet class. This information can
be ?retrieved and set ?using the new scanDates and
scanDates<- ?function respectively. The ?scanDates slot is
designed to hold a ?character vector of length = # ?of
samples, with one character ?element for each sample. (See
help(scanDates) for more ?information.)

In this first round of check-ins we have added affy support
of ?this ?new slot to functions like ReadAffy and we will be
working ?towards ?adding this information to other microarray
platforms as ?well.

This change involved bumping the eSet version number from
1.1.0 ?to ?1.2.0 in the Biobase class definition. In order to
minimize ?the ?impact of this change, the Biobase methods
support both the ?current ?eSet version 1.2.0 as well as old
1.1.0 serialized ?objects so ?updateObject will not be
required to be performed on ?eSet-derived ?objects prior to
use in other functions. We have ?also tested and ?versioned
bumped (and patched where needed) the ?following packages
that create eSet-derived classes to minimize ?any package
build ?issues: ACME, beadarray, beadarraySNP, ?cellHTS2,
CGHbase, codelink, ?crlmm, GeneRegionScan, GGBase, ?maDB,
oligoClasses, ontoTools, puma, ?rMAT, SNPchip, and spkTools.

Below is a demonstration of the new functionality. If you
encounter ?any issues related to this change, please e-mail
this ?list so the ?community can monitor the change.

- The Biocore Team

suppressMessages(library(affy))
example(ReadAffy)

RdAffy> if(require(affydata)){
RdAffy+ ? ? ?celpath <- system.file("celfiles",
package="affydata")
RdAffy+ ? ? ?fns <- list.celfiles(path=celpath,full.names=TRUE)
RdAffy+ ?RdAffy+ ? ? ?cat("Reading ?files:
\n",paste(fns,collapse="\n"),"\n")
RdAffy+ ? ? ?##read a binary celfile
RdAffy+ ? ? ?abatch <- ReadAffy(filenames=fns[1])
RdAffy+ ? ? ?##read a text celfile
RdAffy+ ? ? ?abatch <- ReadAffy(filenames=fns[2])
RdAffy+ ? ? ?##read all files in that dir
RdAffy+ ? ? ?abatch <- ReadAffy(celfile.path=celpath)
RdAffy+ }
Loading required package: affydata
Reading files:
/Library/Frameworks/R.framework/Versions/2.10/Resources/
library/affydata/celfiles/binary.cel ? /Library/Frameworks/
R.framework/Versions/2.10/Resources/library/affydata/celfiles/
text.cel

scanDates(abatch)

? ? ?binary.cel ? ? ? ? ? ?text.cel
"01/23/04 14:30:57" "08/29/03 15:12:30"

sessionInfo()

R version 2.10.0 Under development (unstable) (2009-06-12
r48755)
i386-apple-darwin9.6.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats ? ? graphics ?grDevices utils ? ? datasets
methods ? base
other attached packages:
[1] affydata_1.11.6 affy_1.23.2 ? ? Biobase_2.5.3
loaded via a namespace (and not attached):
[1] affyio_1.13.3 ? ? ? ?preprocessCore_1.7.4 tools_2.10.0

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