r - Preserve column names when ddply returns empty dataframe -

r - Preserve column names when ddply returns empty dataframe -

i using ddply homecoming dataframe, if returned dataframe each element of initial dataframe contains no rows final output empty dataframe 1 column, initial variable. want homecoming empty dataframe columns have returned if did have data.

for illustration if have next

y <- data.frame(a = 1:5, b = 6:10) res1 <- ddply(y, .(a), function(x) subset(x, b == 6)) res2 <- ddply(y, .(a), function(x) subset(x, b == 5))

res1 returns dataframe column & b, whereas res2 returns column - homecoming empty dataframe columns , b.

running next works

res3 <- dlply(y, .(a), function(x) subset(x, b == 5)) res3 <- do.call('rbind', res3)

but there way in 1 go using ddply?

thanks in advance

r plyr