Question

I have the following df called data:

  ProbeID    SampleID ExperimID    Value    
1 2747406        1         2       6.44 
1 2747406        4         2       5.90

etc....

I am trying to extract the Value(s) in col 4 (data[,4]) that match for SampleID = 1 ( data[,2] = 1) and SampleID = 4 (data[,2]=4)

It is important that the values match the SampleID and get extracted together (i.e. for SampleID 1, value = 6.44 and for SampleID 4, value = 5.90). They can get separated into to new df (x and y), ideally giving me x with all the SampleID 1 values and y with all the SampleID 4 values.
I am completely stuck on this, any help is much appreciated.

The goal is to get two new dataframes say x and y to look like depicted below:

With x being:

     SampleID    Value    
1       1        6.44 
etc..

and y being:

    SampleID     Value    
1       4        5.90
etc...

Answer 1

I think you should listen to mnel but if you really want to clutter your workspace up with disjoint bits of data then do this:

 res1 <- dfrm[ dfrm$sampleID == 1 , c("SampleID",    "Value") ]
 res4 <- dfrm[ dfrm$sampleID == 4 , c("SampleID",    "Value") ]