Hi

I am trying to do some data analysis using R and Bioconductor.  I have a
function to read my data called "ReadAffyData" and a function to plot the
data called "preqc".  I want to know if there is any way I can extract
information (read: Data) from the ReadAffyData function into preqc in order
to produce plots? I have not completely understood the inheritance in R and
I am getting errors similar to the one below. I am new to R and could do
with any help in this aspect!

ReadAffyData <- function( filename ) {

        require(affy)
        require(annotate)

        Cov <- read.table( filename, sep="\t", header=1, quote="",
comment="" )
    if( ! all( c( "Filename", "Label", "Repl", "Trt" ) %in% colnames( Cov )
) )
        {
        stop( "Missing mandatory column" )
    }

        Cov <- Cov[order(Cov$Trt),]
        i <- table(Cov$Trt)
        Cov$Repl <- unlist( lapply( i, function( j ) 1:j ) )
        Cov$Label <- paste( as.character( Cov$Trt ), Cov$Repl, sep=":" )
        rownames(Cov) <- as.character(Cov$Label)

        tmp1 <- colnames( Cov )
    tmp2 <- rep( "", length( Cov ) )

        for( i in 1:length( tmp2 ) )
        {
        tmp2[i] <- paste( sort( unique( as.character( Cov[,i] ) ) ),
collapse="/" )
    }

        labelDescription <- data.frame( labelDescription=tmp2 )

    rownames( labelDescription ) <- tmp1
    tmp <- new( "AnnotatedDataFrame", data=Cov,
varMetadata=labelDescription)

        Data <- ReadAffy( sampleNames=as.character( Cov$Label
),phenoData=tmp, verbose=TRUE )
}

preQC <- function(name){
ReadAffyData(name)
plotDensity( log2( pm( Data ) ), xlab="Log2( Intensity )", ylab="Density",
main="Raw(PM)")
}

preQC("cov.txt")
1 reading C:/CEL/GSM311471.CEL ...instantiating an AffyBatch (intensity a
506944x24 matrix)...done.
Reading in : C:/CEL/GSM311471.CEL
Reading in : C:/CEL/GSM311472.CEL
Reading in : C:/CEL/GSM311473.CEL
Reading in : C:/CEL/GSM311474.CEL
Reading in : C:/CEL/GSM311475.CEL
.
.
.
Error in pm(Data) :
  error in evaluating the argument 'object' in selecting a method for
function 'pm': Error: object 'Data' not found

sessionInf()
R version 3.0.1 (2013-05-16)
Platform: i386-w64-mingw32/i386 (32-bit)

locale:
[1] LC_COLLATE=English_India.1252  LC_CTYPE=English_India.1252
 LC_MONETARY=English_India.1252
[4] LC_NUMERIC=C                   LC_TIME=English_India.1252

attached base packages:
[1] parallel  stats     graphics  grDevices utils     datasets  methods
base

other attached packages:
[1] annotate_1.38.0      AnnotationDbi_1.22.6 affy_1.38.1
 Biobase_2.20.0       BiocGenerics_0.6.0

loaded via a namespace (and not attached):
 [1] affyio_1.28.0         BiocInstaller_1.10.1  DBI_0.2-7
IRanges_1.18.1        preprocessCore_1.22.0
 [6] RSQLite_0.11.4        stats4_3.0.1          tools_3.0.1
XML_3.96-1.1          xtable_1.7-1
[11] zlibbioc_1.6.0



Thanking you,
Ipsitha
Graduate Student
London

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