Extracts a Subset of Rows from a Data Frame
The function extracts a subset of rows, and columns if required, from a data frame and returns the subset as a new data frame based on the criterion provided by the user. Unused factor names are dropped.
gx.subset(dfname, subset = TRUE)
dfname |
name of the data frame from which rows are to be extracted. |
subset |
the criterion for selecting the subset (rows). |
The subset criterion can be ‘complex’ and be a combination of conditions, see Examples below.
data |
a data frame only containing the rows of the input data frame where the criterion is met. |
This function is based on a script shared by Bill Venables on S-News, October 10, 1997. As such it may pre-date the time that subset was added to the S-Plus library. It is simple to use and has been retained.
William N. Venables
## Make test data available data(kola.c) ## Make a subset of the data for Finland finland.c <- gx.subset(kola.c, COUNTRY == "FIN") ## Make a subset of the data for rock type, LITHO 82 occurring ## in Russia. Note that both COUNTRY and LITHO are factor variables russia.82 <- gx.subset(kola.c, COUNTRY == "RUS" & LITHO == 82) ## Make a subset of the data for Cu exceeding 50(ppm) in Norway norway.cugt50 <- gx.subset(kola.c, COUNTRY == "NOR" & Cu >50) ## Make single element subsets, e.g. for use with function gx.cnpplts ## First locate the column in the data frame where the element of ## interest is stored using dimnames(kola.c)[[2]], we find that Be is ## the 19th column in the data frame dimnames(kola.c)[[2]] Norway <- gx.subset(kola.c,COUNTRY=="NOR")[,19] Russia <- gx.subset(kola.c,COUNTRY=="RUS")[,19] Finland <- gx.subset(kola.c,COUNTRY=="FIN")[,19] ## Clean-up rm(finland.c) rm(russia.82) rm(norway.cugt50) rm(Norway) rm(Russia) rm(Finland)
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