fortify.tis {tis} | R Documentation |
A fortify method for tis objects
## S3 method for class 'tis': fortify(x, offset = 0.5, dfNames=ifelse(is.null(dim(x)), as.character(substitute(x)), NA))
x |
A tis object of time series |
offset |
A number between 0 and 1 specifying where in the period of time
represented by the 'ti(x)' the points should eventually be plotted in ggplot2 .
'offset = 0' gives the beginning of the period and 'offset
= 1' the end of the period, 'offset = 0.5' the middle of the period, and
so on. For example if x is a tis object of quarterly time series and offset = 0.5
then the resulting plotted points would fall in the middle of each quarter.
offset is passed on to POSIXct(ti(x), offset=offset)
and used to create the field date in the resulting data frame.
|
dfNames |
A character vector of the names for the tis objects contained in x . Defaults to the name of the tis object in the univariate case and the column names of the tis object in the multivariate case. |
This function turns a tis
object into a data frame containing the original time series plus a field of dates, called date
and adjusted by an ‘offset’,
so that the time series can be more easily plotted with ggplot2
.
Trevor Davis
## Not run: # Examples of plotting tis series with ggplot2 require("datasets") require("ggplot2") # univariate example num_discoveries <- as.tis(discoveries) ggplot(data = fortify(num_discoveries, offset=0)) + geom_line(aes(x=date, y=num_discoveries)) + scale_x_date(major="10 years") # multivariate example using the "melt trick" Seatbelts.tis <- as.tis(Seatbelts[ , c("drivers", "front", "rear")]) Seatbelts.df <- fortify(Seatbelts.tis) Seatbelts.dfm <- melt(Seatbelts.df, id.var = "date", variable_name="type") qplot( date, value, data = Seatbelts.dfm, geom="line", group=type, colour=type, linetype=type ) + geom_vline(xintercept=as.numeric(as.Date("1983-01-31")), colour="black", linetype="dashed") + ylab("Road Casulties in the UK") ## End(Not run)