using a function with lapply to create a column and match values - r

Question

I have two datasets H and G. They have a column named 'diff' that as the name suggests, holds difference between two columns within each dataset. I used lapply to calculate the percentage for each dataset (I have more datasets than H and G, so would like to calculate the percentage of the two columns in each dataset), but for some reason lapply gives me the output however doesn't create "perc" column in the datasets that pass through it. What am I doing wrong here?
H<-data.frame(replicate(10,sample(0:20,10,rep=TRUE)))
G<-data.frame(replicate(10,sample(0:20,10,rep=TRUE)))
H[c(2,3,7,9),9]<-NA
G[c(1,5,7,8),9]<-NA
H$diff<-H$X10-H$X9
G$diff<-G$X10-G$X9
dsay<-list(H,G)
lapply(dsay,function(x)x$perc<-round((x$diff/x$X10)*100,1))
Extension of this question:
once I have the percent differences as columns using:
H<-data.frame(replicate(10,sample(0:20,10,rep=TRUE)))
G<-data.frame(replicate(10,sample(0:20,10,rep=TRUE)))
H[c(2,3,7,9),9]<-NA
G[c(1,5,7,8),9]<-NA
H$diff<-H$X10-H$X9
G$diff<-G$X10-G$X9
H$perc<-round((H$diff/H$X10)*100,1)
G$perc<-round((G$diff/G$X10)*100,1)
I generated a plot using:
xyplot(X8+X9+X10~X1,H,type=c('p','l','g'),
col = c('yellow', 'green', 'blue','red'),
ylab='Count',layout=c(3, 1),
xlab=paste("H",'difference',min(pmin(H$perc, na.rm = TRUE),na.rm=TRUE),
'% change count'))
Never mind the plot it will generate, but what I'm trying to get to is that I also display the value of corresponding difference from the "diff" column alongwith the lowest difference (which is what the min function is doing). I've tried using "match" in vain. Could someone help please?

Answer 1

If we need the changes to reflect in the dataframe objects as well, list2env or assign can be used. But, I would do all the computations within the list itself.
list2env(lapply(mget(c('H','G')), function(x)
{x$perc<-round((x$diff/x$X10)*100,1);x}), envir=.GlobalEnv)