Hi, On Sep 8, 2009, at 9:06 AM, Robin Hankin wrote:
Hi I deal with long vectors almost all of whose elements are zero. Typically, the length will be ~5e7 with ~100 nonzero elements. I want to deal with these objects using a sort of sparse vector.
Would using sparse matrices (from the Matrix or SparseM packages) be overkill?
-steve
The problem is that I want to be able to 'add' two such vectors. Toy problem follows. Suppose I have two such objects, 'a' and 'b': > a $index [1] 20 30 100000000 $val [1] 2.2 3.3 4.4 > b $index [1] 3 30 $val [1] 0.1 0.1 > What I want is the "sum" of these: > AplusB $index [1] 3 20 30 100000000 $val [1] 0.1 2.2 3.4 4.4 > See how the value for index=30 (being common to both) is 3.4 (=3.3+0.1). What's the best R idiom to achieve this? -- Robin K. S. Hankin Uncertainty Analyst University of Cambridge 19 Silver Street Cambridge CB3 9EP 01223-764877 ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
-- Steve Lianoglou Graduate Student: Computational Systems Biology | Memorial Sloan-Kettering Cancer Center | Weill Medical College of Cornell University Contact Info: http://cbio.mskcc.org/~lianos/contact ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
