Replace Function (How to replace numbers in a data frame with a specific number)

taxa <- (structure(list(Date = structure(c(4L, 4L, 4L, 4L, 4L, 4L, 4L,
4L, 4L, 4L, 4L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L), .Label = c("2006/04",
"2006/05", "2006/07", "2006/10", "2006/12", "2007/02", "2007/04",
"2007/06", "2007/08", "2007/10", "2007/12", "2008/01"), class = "factor"),
    RiverMile = c(61L, 119L, 148L, 179L, 185L, 187L, 190L, 196L,
    198L, 202L, 215L, 61L, 119L, 148L, 179L, 185L, 187L, 190L,
    196L, 198L), Site = structure(c(9L, 1L, 2L, 3L, 4L, 10L,
    5L, 11L, 6L, 7L, 8L, 9L, 1L, 2L, 3L, 4L, 10L, 5L, 11L, 6L
    ), .Label = c("119", "148", "179", "185", "190", "198", "202",
    "215", "61", "BC", "HC", "SC"), class = "factor"), location =
structure(c(2L,
    2L, 2L, 2L, 2L, 1L, 2L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
    1L, 2L, 1L, 2L), .Label = c("creek", "river"), class = "factor"),
    Amphipoda = c(0, 0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 0, 0, 1,
    0, 1, 1, 0, 1), Coleoptera = c(1, 1, 4, 1, 0, 1, 1, 2, 1,
    2, 0, 0, 0, 1, 1, 0, 0, 0, 2, 1), Decapoda = c(0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1), Diptera = c(6,
    6, 14, 3, 16, 10, 12, 0, 3, 9, 6, 5, 3, 10, 0, 9, 3, 11,
    2, 8), Ephemeroptera = c(5, 6, 4, 1, 3, 1, 3, 1, 0, 2, 0,
    2, 2, 2, 0, 0, 0, 0, 1, 0)), .Names = c("Date", "RiverMile",
"Site", "location", "Amphipoda", "Coleoptera", "Decapoda", "Diptera",
"Ephemeroptera"), row.names = c("61 2006/10", "119 2006/10",
"148 2006/10", "179 2006/10", "185 2006/10", "BC 2006/10", "190 2006/10",
"HC 2006/10", "198 2006/10", "202 2006/10", "215 2006/10", "61 2006/12",
"119 2006/12", "148 2006/12", "179 2006/12", "185 2006/12", "BC 2006/12",
"190 2006/12", "HC 2006/12", "198 2006/12"), class = c("cast_df",
"data.frame")))

replace(taxa, taxa>0, 1)

#Is preforms as I would like except that I only want to do this on
columns 5:19 and I can't just use

replace(taxa, taxa[,5:19]>0, 1)

#any suggestions

Stephen Sefick