Description Usage Arguments Details Value Note Author(s) References See Also Examples
This function converts a DataTreeSet
into an ExprTreeSet
using the Factor Analysis for Robust Microarray Summarization (FARMS) method.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 |
xps.data |
object of class |
filename |
file name of ROOT data file. |
filedir |
system directory where ROOT data file should be stored. |
tmpdir |
optional temporary directory where temporary ROOT files should be stored. |
normalize |
logical. If |
weight |
hyperparameter, usually set to 0.5 for |
mu |
hyperparameter allowing to correct for potential bias. |
scale |
scaling parameter, usually set to 1.0 for |
tol |
termination tolerance for EM algorithm. |
cyc |
maximum number of cycles of EM algorithm. |
weighted |
logical, used only with |
version |
version of original farms package. Currently, |
option |
option determining the grouping of probes for summarization, one of ‘transcript’, ‘exon’, ‘probeset’; exon arrays only. |
exonlevel |
exon annotation level determining which probes should be used for summarization; exon/genome arrays only. |
xps.scheme |
optional alternative |
add.data |
logical. If |
verbose |
logical, if |
This function computes the FARMS (Factor Analysis for Robust Microarray Summarization) expression measure described in Hochreiter et al. for both expression arrays and exon arrays.
Parameter version
currently allows the user to choose between the original implementation
of FARMS as implemented in package ‘farms_1.3.0’ or enhanced FARMS as implemented in
package ‘farms_1.3.1’. By default version="1.3.1"
is used.
Parameter weight
is a hyperparameter which determines the influence of the prior. For
version="1.3.1"
the value in the range of [0,1].
Parameter mu
is a hyperparameter which allows to quantify different aspects of potential
prior knowledge. Values near zero assume that most genes do not contain a signal and introduce
a bias for loading matrix elements near zero.
Parameter weighted
is a logical and indicates whether a weighted mean or a least square
fit is used to summarize the loading matrix. It is applicable only to version="1.3.1"
.
For exon arrays it is necessary to supply the requested option
and exonlevel
.
Following option
s are valid for exon arrays:
transcript : | expression levels are computed for transcript clusters, i.e. probe sets containing the same 'transcript_cluster_id'. |
exon : | expression levels are computed for exon clusters,
i.e. probe sets containing the same 'exon_id', where each exon cluster
consists of one or more probeset s. |
probeset : | expression levels are computed for individual probe sets, i.e. for each 'probeset_id'. |
Following exonlevel
annotations are valid for exon arrays:
core : | probesets supported by RefSeq and full-length GenBank transcripts. | |
metacore : | core meta-probesets. | |
extended : | probesets with other cDNA support. | |
metaextended : | extended meta-probesets. | |
full : | probesets supported by gene predictions only. | |
metafull : | full meta-probesets. | |
affx : | standard AFFX controls. | |
all : | combination of above (including affx). |
Following exonlevel
annotations are valid for whole genome arrays:
core : | probesets with category 'unique', 'similar' and 'mixed'. | |
metacore : | probesets with category 'unique' only. | |
affx : | standard AFFX controls. | |
all : | combination of above (including affx). |
Exon levels can also be combined, with following combinations being most useful:
exonlevel="metacore+affy" : | core meta-probesets plus AFFX controls |
exonlevel="core+extended" : | probesets with cDNA support |
exonlevel="core+extended+full" : | supported plus predicted probesets |
Exon level annotations are described in the Affymetrix whitepaper exon_probeset_trans_clust_whitepaper.pdf:
“Exon Probeset Annotations and Transcript Cluster Groupings”.
In order to use an alternative SchemeTreeSet
set the corresponding SchemeSet xps.scheme
.
An ExprTreeSet
The expression measure obtained with FARMS is given in linear scale, analogously to the expression
measures computed with mas5
and rma
.
For the analysis of many exon arrays it may be better to define a tmpdir
, since this will
store only the results in the main file and not e.g. background and normalized intensities, and
thus will reduce the file size of the main file. For quantile normalization memory should not
be an issue, however DFW depends on RAM unless you are using a temporary file.
Christian Stratowa
Hochreiter, S., Clevert D.-A., and Obermayer, K. (2006), A new summarization method for Affymetrix probe level data. Bioinformatics 22(8):943-949
1 2 3 4 5 6 7 8 9 | ## first, load ROOT scheme file and ROOT data file
scheme.test3 <- root.scheme(paste(path.package("xps"),"schemes/SchemeTest3.root",sep="/"))
data.test3 <- root.data(scheme.test3, paste(path.package("xps"),"rootdata/DataTest3_cel.root",sep="/"))
data.farms <- farms(data.test3,"tmp_Test3FARMS",verbose=FALSE)
## get data.frame
expr.farms <- validData(data.farms)
head(expr.farms)
|
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