Adai, I suspect that Xiaofan was looking for the use of a function like subset(), which of course does enable one to specify filtering criteria and return a subset of rows in a data frame that satisfy the criteria.
I am presuming that the SQL reference was more towards using SQL Select/Where type statements within a database as an example, as opposed to wanting to query a SQL database from within R. Xiaofan, see ?subset for more information. The function will also let you specify a subset of columns using the 'select' argument. In addition to subset(), there is also the use of [.data.frame, which will enable you to specify criteria using the typical "[row, column]" extraction approach. See ?"[.data.frame" for more information. Which approach is taken is to some extent personal preference. I find it easier to use subset() when the criteria are more complex boolean expressions and/or where I only want a subset of the columns. HTH, Marc Schwartz On Sun, 2005-11-06 at 17:44 +0000, Adaikalavan Ramasamy wrote: > Check out the R Data Import/Export manual, especially > http://cran.r-project.org/doc/manuals/R-data.html#DBI-_002f-RMySQL > and the RMySQL package. > > > On Sun, 2005-11-06 at 03:37 +0000, Xiaofan Li wrote: > > Dear colleague, > > > > Is it able in R to manipulate data tables as in SQL-based databases? > > Is there any good method in R to locate a special subset of data rows, which > > satisfy a certain expression of restrictions (e.g. dataTable$peakValue < > > 3.0)? Then if located, is it able for manipulations, for example, to delete > > them from the dataTable? > > > > Cheers, > > Xiaofan > > ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html