[R] How to sum some columns based on their names

[Kuma Raj]

I want to sum columns based on their names. As an exampel how could I
sum columns which contain 6574, 7584 and 85 as column names?  In
addition, how could I sum those which contain 6574, 7584 and 85 in
ther names and have a prefix "f". My data contains several variables
with

I want to sum columns based on their names. As an exampel how could I
sum columns which contain 6574, 7584 and 85 as column names?  In
addition, how could I sum those which contain 6574, 7584 and 85 in
ther names and have a prefix "f". My data contains several variables
with

dput(df1)
structure(list(date = structure(c(1230768000, 1230854400, 1230940800,
1231027200, 1231113600, 1231200000, 1231286400, 1231372800, 1231459200,
1231545600, 1231632000), class = c("POSIXct", "POSIXt"), tzone = "UTC"),
    f014card = c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0), f1534card = c(0,
    1, 1, 0, 0, 1, 0, 0, 1, 0, 1), f3564card = c(1, 6, 1, 5,
    5, 4, 4, 7, 6, 4, 6), f6574card = c(3, 6, 4, 5, 5, 2, 10,
    3, 4, 2, 4), f7584card = c(13, 6, 1, 4, 10, 6, 8, 12, 10,
    4, 3), f85card = c(5, 3, 1, 0, 2, 10, 7, 9, 1, 7, 3), m014card = c(0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0), m1534card = c(0, 0, 1, 0,
    0, 0, 0, 1, 1, 1, 0), m3564card = c(12, 7, 4, 7, 12, 13,
    12, 7, 12, 2, 11), m6574card = c(3, 4, 8, 8, 8, 10, 7, 6,
    7, 7, 5), m7584card = c(8, 10, 5, 4, 12, 7, 14, 11, 9, 1,
    11), m85card = c(1, 4, 3, 0, 3, 4, 5, 5, 4, 5, 0)), .Names = c("date",
"f014card", "f1534card", "f3564card", "f6574card", "f7584card",
"f85card", "m014card", "m1534card", "m3564card", "m6574card",
"m7584card", "m85card"), class = "data.frame", row.names = c("1",
"2", "3", "4", "5", "6", "7", "8", "9", "10", "11"))