HI,

I got a SummarizedExperiment file and would like to extract gene expression for further analysis. However, there is no name for the assay, how I can change the name or subset data. Thank you

data

class: SummarizedExperiment 
dim: 15093 100 
metadata(0):
assays(1): ''
rownames(15093): ENSG00000000003 ENSG00000000419 ... ENSG00000273488 ENSG00000273489
rowData names(3): Ensembl_ID GeneID EntrezID 
colnames(100): 1 2 3 ... 99 100
colData names(14): number age ... status

assayNames(data)

NULL

assay(data, " ")[1:3,1:3]

'assay(<SummarizedExperiment>, i="character", ...)' invalid subscript 'i'
'''' not in names(assays(<SummarizedExperiment>))

If I want to subset data@assays[[1]]

Error in data@assays[[1]] : this S4 class is not subsettable

Whenever you need to know something about an S4 class, you can (usually) do something like

?SummarizedExperiment-class

And which brings up the help page, which includes this

Usage:

     ## Constructor

     # See ?RangedSummarizedExperiment for the constructor function.

     ## Accessors

     assayNames(x, ...)
     assayNames(x, ...) <- value
     assays(x, withDimnames=TRUE, ...)
     assays(x, withDimnames=TRUE, ...) <- value

And further down, this

Accessors:

     In the following code snippets, 'x' is a SummarizedExperiment
     object.

     'assays(x)', 'assays(x) <- value': Get or set the assays. 'value'
          is a 'list' or 'SimpleList', each element of which is a
          matrix with the same dimensions as 'x'.

     'assay(x, i)', 'assay(x, i) <- value': A convenient alternative
          (to 'assays(x)[[i]]', 'assays(x)[[i]] <- value') to get or
          set the 'i'th (default first) assay element. 'value' must be
          a matrix of the same dimension as 'x', and with dimension
          names 'NULL' or consistent with those of 'x'.

     'assayNames(x)', 'assayNames(x) <- value': Get or set the names of
          'assay()' elements.

Which I believe answers your question.

Here's a no-name SummarizedExperiment

> se = SummarizedExperiment(matrix(1:10, 5))
> se
class: SummarizedExperiment
dim: 5 2
metadata(0):
assays(1): ''
rownames: NULL
rowData names(0):
colnames: NULL
colData names(0):

accessing the single assay is easy

> assay(se)
     [,1] [,2]
[1,]    1    6
[2,]    2    7
[3,]    3    8
[4,]    4    9
[5,]    5   10

as is subsetting

> assay(se[1:2,])
     [,1] [,2]
[1,]    1    6
[2,]    2    7