r - Find error in columns for every dataframe in list -

i have list of dataframes stored in list c. find differences between columns, example (actual-pred1.a, actual-pred2.a, on) every dataframe in list. have 100 dataframes in list have same. have written following example data , code below find it.

a<-data.frame(pred1.a=c(4,3,32,2,3), pred2.a=c(5,3,2,6,22),pred3.a=c(3,2,7,1,23),actual=c(8,9,2,6,21)) b<-data.frame(pred1.b=c(3,6,6,2,5), pred2.b=c(2,7,8,4,23),pred3.b=c(1,4,7,3,22),actual=c(9,2,1,3,25))  c<-list(a,b)  i3<-1:3 error <- list()  (iter in 1:length(c)){   (i in seq_along(i3)){     error<-sqrt(mean((c[[iter]][4]-c[[iter]][i])^2))   } } 

i want error value such error[[1]][1](error value dataframe1:actual-pred1.a),error[[1]][2],error[[1]][3], error[[2]][1].

and there way unlist? because have list contains 100 dataframes.

making minor changes @richscriven's suggestion it's easy errors in separate columns, keeping originals intact:

df_list <- list(a,b)  lapply(df_list, function(df) {     errors = df$actual - df[1:3]     colnames(errors) = paste0("err_", colnames(df)[1:3])     cbind(df, errors)     } ) 

output:

[[1]]   pred1.a pred2.a pred3.a actual err_pred1.a err_pred2.a err_pred3.a 1       4       5       3      8           4           3           5 2       3       3       2      9           6           6           7 3      32       2       7      2         -30           0          -5 4       2       6       1      6           4           0           5 5       3      22      23     21          18          -1          -2  [[2]]   pred1.b pred2.b pred3.b actual err_pred1.b err_pred2.b err_pred3.b 1       3       2       1      9           6           7           8 2       6       7       4      2          -4          -5          -2 3       6       8       7      1          -5          -7          -6 4       2       4       3      3           1          -1           0 5       5      23      22     25          20           2           3 

as mentioned c not great name variable i've renamed here.