Subsetting a data frame

db <- structure(list(ind = c("ind1", "ind2", "ind3", "ind4"), test1 = c(1,

terms_include <- c("1","2","3")
terms_exclude <- c("1.1","1.2","1.3")

f.match <- function(obj, inc, exc){

db

f.match(db, terms_include, terms_exclude)

Hi R users,

I really need help with subsetting ?data frames:

I have a large database of medical records and I want to be able to match
patterns from a list of search terms .

I've used this simplified data frame in a previous example:


db <- structure(list(ind = c("ind1", "ind2", "ind3", "ind4"), test1 = c(1,
2, 1.3, 3), test2 = c(56L, 27L, 58L, 2L), test3 = c(1.1, 28,
9, 1.2)), .Names = c("ind", "test1", "test2", "test3"), class =
"data.frame", row.names = c(NA,
-4L))

terms_include <- c("1","2","3")
terms_exclude <- c("1.1","1.2","1.3")


So in this example I want to include all the terms from terms include as
long as they don't occur with terms exclude in the same row of the data
frame.

Previously I was given this function which works very well if you want to
match exactly:


f <- function(x) ?!any(x %in% terms_exclude) && any(x %in% terms_include)
db[apply(db[, -1], 1, f), ]

? ind test1 test2 test3
2 ind2 ? ? 2 ? ?27 ?28.0
4 ind4 ? ? 3 ? ? 2 ? 1.2


I would like to know if there is a way to write a similar function that
looks for matches that start with the query string: ?as in
grepl("^pattern",x)

I started writing a function but am not sure how to get it to return the
dataframe or matrix:


for (i in 1:length(terms_include)){
db_new <- apply(db,2, grepl,pattern=i)
}

Applying this function gives me:

db_new <- structure(c(FALSE, FALSE, TRUE, FALSE, FALSE, FALSE, TRUE, TRUE,
FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE), .Dim = c(4L,
4L), .Dimnames = list(NULL, c("ind", "test1", "test2", "test3"
)))

So the above is searching the pattern anywhere in the dataframe instead of
just at the beginning of the string.

How would I incorporate look for terms to include but don't return the row
of the data frame if it also includes one of the terms to exclude while
using partial matching?

I hope that this makes sense.

Many thanks,
Natalie

-----
Natalie Van Zuydam

PhD Student
University of Dundee
nvanzuydam at dundee.ac.uk
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