R: using lapply with data frames and custom function

Question

I have a question about using lapply with lists of dataframes. Suppose I have two lists:

 list1<-list(data1,data2)
 list2<-list(data3,data4)

I want to write a function that appends a column and row from one dataframe to another. This is my function:

append<-function(origin.data, destin.data){

vec.to.append<-origin.data[,1]

#add as the first column
destin.data<-cbind(vec.to.append, destin.data)

#add as first row
vec.to.append<-t(c(0, vec.to.append))
destin.data<-rbind(vec.to.append, destin.data)

return(destin.data)
}

This works fine if I run

append(list1[[1]], list2[[1]])

or

append(list1[[2]], list2[[2]])

but gives me an error when I try to use lapply:

trial<-lapply(list1, append, destin.data=list2)

The error looks straightforward:

Error in rbind(vec.to.append, destin.data) : number of columns of matrices must match (see arg 2)

but as I checked the dimensions of my dataframes and vector, all looked fine. Plus, the function runs and gives the expected result if I do not use lapply but do it "argument by argument". Can somebody help me out?

By the way, I saw the answer here: Using lapply with changing arguments but applying my function over the list names gives an empty result:

prova<-lapply(names(list1), append, destin.data=list2)

prova
list()

Clearly, I am missing something!

Answer 1

lapply(list1, append, destin.data=list2) is equivalent to:

list(append(list1[[1]], list2),
     append(list1[[2]], list2)

Which is not what you want. If you want to pair up list1 and list2, element-wise, you should do:

lapply(seq_along(list1), function(i) append(list1[[i]], list2[[i]])

This is equivalent to:

list(append(list1[[1]], list2[[1]]),
     append(list1[[2]], list2[[2]])

which is what you do want, right?

edit: as the other answer says, you can also use mapply, which is a little tidier, but this is the lapply-based solution. Result is the same in either case.