Need help on parsing dates
Ajay Shah wrote:
I know this:
> library(date) > x="1979-04-04" > try=as.date(x, "ymd") > print(try)
[1] 4Apr79 and that `x' here has to be a string, e.g.:
> x=1979-04-04 > print(x)
[1] 1971 I'm stuck in reading from a file. I say:
> A <- read.table(file="try") > print(A)
V1 V2 1 1979-04-04 -1.04712042 2 1979-04-06 0.54538055 3 1979-04-09 0.09663392 4 1979-04-11 0.57119871 5 1979-04-12 0.73594112 6 1979-04-17 -1.54422087 7 1979-04-18 -0.20595691 8 1979-04-19 0.12700429 9 1979-04-20 0.42016807 10 1979-04-23 -1.46838241 I am confused - is V1 a number or a string? Looking at it, it must be a string. But yet:
> library(date) > try=as.date(A$V1, "ymd")
Error in as.date(A$V1, "ymd") : Cannot coerce to date format In short, how do I parse in dates of the format yyyy-mm-dd (the ISO 8601 format) or the yyyymmdd format. And if I may ask the next step: How do I tell R that I have a file full of data all of which is time-series data, where V1 is the datetime vector, and all the other columns are time-series, to do things like ARMA models and ts plots with?
To see what class a column in a data.frame is the best way is to try: sapply(A, data.class) My guess is that "V1" is being read in as a factor (default). To convert to character to use with as.date, then use as.date(as.character(A$V1), "ymd") BTW, I would avoid using "try" as a variable name since "try" is a function in the base package. As for you second question, see the package ts for ARIMA modeling. -sundar