Question: How can I reassign assayData slot of ExpressionSet?
gravatar for wangshx
2.4 years ago by
China/Shanghai/ShanghaiTech. University
wangshx10 wrote:

When I use exprs function to reassign expression matrix to an ExpressionSet object, it does not work and an error occur. I want to remove the rows which cannot match any gene symbol.

A minimal code as follows can reproduce my error, someone who know how to do this correctly please help me, thanks.

> dataDirectory <- system.file("extdata", package="Biobase")
> exprsFile <- file.path(dataDirectory, "exprsData.txt")
> exprs <- as.matrix(read.table(exprsFile, header=TRUE, sep="\t",
+                               row.names=1,
> minimalSet <- ExpressionSet(assayData=exprs)
> sdata <- matrix(0, nrow=400, ncol=26)
> exprs(minimalSet) <- sdata
Error in .validate_assayDataElementReplace(obj, value) : 
  object and replacement value have different dimensions
> exprs(minimalSet) <- NULL  # here I want to assign NULL to arrayData and reassign sdata to it, but it fails
Error in (function (classes, fdef, mtable)  : 
  unable to find an inherited method for function ‘exprs<-’ for signature ‘"ExpressionSet", "NULL"’
ADD COMMENTlink modified 2.4 years ago by Kevin Blighe60k • written 2.4 years ago by wangshx10
gravatar for Kevin Blighe
2.4 years ago by
Kevin Blighe60k
Kevin Blighe60k wrote:

If you are filtering genes or samples from an ExpressionSet object, you do not have to access via the exprs() function. Just filter based on the name of the ExpressionSet object:


ExpressionSet (storageMode: lockedEnvironment)
assayData: 194706 features, 22 samples


Select first 10 features and samples


ExpressionSet (storageMode: lockedEnvironment)
assayData: 10 features, 10 samples

If you're trying to re-assign an entire 'new' expression matrix to your ExpressionSet object, then I do not see the utility in this. Just create another ExpressionSet object based on the new data matrix.

ADD COMMENTlink modified 14 days ago • written 2.4 years ago by Kevin Blighe60k

Thank a lot. Your suggestion is practical.

ADD REPLYlink written 2.4 years ago by wangshx10
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