Add time series objects compability

[mamut86]

TS object compatibility would ensure that the plots and outputs also handle date information. There is also a bug that actuals are not shown in the plot when entered as TS object

dataSafari <- ts(tsSafari[,-1],frequency=12,start=c(2009,1));
safari6 <- dataSafari[,8];
safari6 <- window(safari6,start=time(safari6)[which(safari6!=0)[1]]);
plot(diffusion(safari6))
plot(diffusion(dataSafari[,8]))

[mamut86]

plot fixed

Should there be a option that forecasts are also ts object if input is?