dataframe - Trying to map timestamps to dates in R data frame -


i have data frame df column time contains timestamps , function from.timestamp

from.timestamp = function(timestamp) {   return(as.posixlt(timestamp/1e3, origin="1970-01-01 00:00:00 gmt")) }

that converts timestamp date type. how modify data frame timestamps converted dates?

my approach

i'm trying following:

df$time <- apply(as.array(df$time), margin=1, fun=from.timestamp)

the resulting column entries time not date, rather sequence of numbers, e.g., 1.034, 59.000, 23.000, 7.000, 5.000, 113.000, 5.000, 157.000, 1.000.

dput(df) gives:

structure(list(time = c(1370674741034, 1372671995085, 1370847555008, 1371456058556, 1372570911379, 1371937835807)), .names = "time", row.names = 8831395:8831400, class = "data.frame")

just do

df$time <- from.timestamp(df$time)

the reason you're getting strange behaviour because posixlt objects lists, components year, month, day, etc. in code, apply receives from.timestamp sequence of lists, combines single list. in doing so, strips class information result, why saw odd numbers. these odd numbers individual components of posixlt object representing datetime: seconds, minutes, hour, day of month, month, year, weekday, day in year.


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