The full error that you got after typing:
mchart1<-gvisMotionChart(ChickWeight1,idvar='weight',timevar='Time')
was:
Error in gvisCheckMotionChartData(data, my.options) :
The data must have rows with unique combinations of idvar and timevar.
Your data has 578 rows, but idvar and timevar only define 375 unique rows.
In addition: Warning message:
In if (class(x[[.x]]) == "Date") as.character(x[[.x]]) else x[[.x]] :
the condition has length > 1 and only the first element will be used
This error would have clued you in to the fact that you hadn't designated the ids of the chicks. If you do mchart1<-gvisMotionChart(ChickWeight,idvar='Chick',timevar='Time')
This will give you the motion plot of how the chicks gain weight over time.
?gvisMotionChart
is very useful.