[R] Overlaying graphs from different datasets with ggplot

[MUHC-Research]

Dear R-users,

I recently began using the ggplot2 package and I am still in the process of
getting used to it.

My goal would be to plot on the same grid a number of curves derived from
two distinct datasets. The first dataset (called molten.data) looks like
this :

Column names : Perc, Week, Weight

P10   21  333.3554
P90   21  486.0480
P10   22  452.6347
P90   22  563.8263
P10   23  575.0960
P90   23  661.6841
P10   24  700.4449
P90   24  779.4067
P10   25  828.4966
P90   25  917.1222

The second dataset (called skj) looks like this:

Column names : Week, Perc, Weight
 
21    1  317.5    
22    1  392.5    
23    1  467.5    
24    1  542.5    
25    1  617.5    
26    1  697.5    
21    2  535.0    
22    2  632.5    
23    2  737.5    
24    2  855.0    
25    2  980.0    
26    2 1115.0   
21    3  425.0    
22    3  512.5    
23    3  602.5    
24    3  697.5    
25    3  800.0    
26    3  907.5    

Now, I plot my graphs using (with the Perc column in skj being a factor) :

p <- ggplot(molten.data, aes(x=Week, y=Weight, group=Perc)) ;
p <- p + geom_line(aes(colour = Perc,size=1,linetype=Perc)) ;
p +
geom_line(data=skj,mapping=aes(x=Week,y=Weight,group=Perc,linetype=Perc)) ;

This yields the following error message:
##
Error in data.frame(c("#FF6C91FF", "#00C1A9FF"), c("solid", "22", "42",  : 
  arguments imply differing number of rows: 2, 5
##

If I remove the linetype=Perc argument, I get a graph, but also a warning:
##
Warning message:
In data$arrow <- NULL : Coercing LHS to a list
##

So, what am I doing wrong in this situation?

I thank you sincerely for your help,

Luc
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