"unlist" a list stored in a variable - r

Question

I have a dataframe with a two odd variables. For one one variable, each cell stores a list whose contents is simply a vector of two numbers. For the other variable, each cell stores a three dimensional array (even though only two dimensions are necessary) of 8 numbers.
I want to simplify the dataset by breaking out the odd variable into separate variables. I figured out how to break all the data out using a for loop but this is very slow. I know apply is supposed to be generally quicker, but I can't figure out how I would translate this to apply. Is it possible, or is there a better way to do this?
for (i in 1:nrow(df)){
if (length(df$coordinates.coordinates[[i]]>0)){
df[i,"coordinates.lon"]<- df$coordinates.coordinates[[i]][1]
df[i,"coordinates.lat"]<- df$coordinates.coordinates[[i]][2]
}
if (length(df$place.bounding_box.coordinates[[i]]>0)){
df[i,"place.bounding_box.a.lon"] <-df$place.bounding_box.coordinates[[i]][1,1,1]
df[i,"place.bounding_box.b.lon"] <-df$place.bounding_box.coordinates[[i]][1,2,1]
df[i,"place.bounding_box.c.lon"] <-df$place.bounding_box.coordinates[[i]][1,3,1]
df[i,"place.bounding_box.d.lon"] <-df$place.bounding_box.coordinates[[i]][1,4,1]
df[i,"place.bounding_box.a.lat"] <-df$place.bounding_box.coordinates[[i]][1,1,2]
df[i,"place.bounding_box.b.lat"] <-df$place.bounding_box.coordinates[[i]][1,2,2]
df[i,"place.bounding_box.c.lat"] <-df$place.bounding_box.coordinates[[i]][1,3,2]
df[i,"place.bounding_box.d.lat"] <-df$place.bounding_box.coordinates[[i]][1,4,2]
}
}
EDIT
Here is an example dataframe with one case (via dput)
structure(list(coordinates.coordinates = list(c(112.088477, -7.227974
)), place.bounding_box.coordinates = list(structure(c(112.044456,
112.044456, 112.143242, 112.143242, -7.263067, -7.134563, -7.134563,
-7.263067), .Dim = c(1L, 4L, 2L)))), .Names = c("coordinates.coordinates",
"place.bounding_box.coordinates"), class = c("tbl_df", "data.frame"
), row.names = c(NA, -1L))
In case it helps, this is the data format that gets out when you try to read Twitter stream data using jsonlite's stream_in function (with flatten=TRUE)

Answer 1

library(dplyr)
df = data_frame(
coordinates.coordinates =
list(c(0, 1), c(2, 3)),
place.bounding_box.coordinates =
list(array(0, dim=c(1, 4, 2)),
array(1, dim=c(1, 4, 2))))
df %>%
rowwise %>%
do(with(., data_frame(
longitude = coordinates.coordinates[1],
latitude = coordinates.coordinates[2]) %>% bind_cols(
place.bounding_box.coordinates %>%
as.data.frame %>%
setNames(c(
"place.bounding_box.a.lon",
"place.bounding_box.b.lon",
"place.bounding_box.c.lon",
"place.bounding_box.d.lon",
"place.bounding_box.a.lat",
"place.bounding_box.b.lat",
"place.bounding_box.c.lat",
"place.bounding_box.d.lat")))))