R Creating Dynamic variables from group aggregated set of DataFrames - r

Question

My problem statement is I have a list of dataframes as df1,df2,df3.Data is like
df1
a,b,c,d
1,2,3,4
1,2,3,4
df2
a,b,c,d
1,2,3,4
1,2,3,4
Now, for these two dataframe I should create a new dataframe taking aggregated column of those two dataframes ,for that I am using below code
for(i in 1:2){
assign(paste(final_val,i,sep=''),sum(assign(paste(df,i,sep='')))$d*100)}
I am getting the error:
Error in assign(paste(hvp_route_dsct_clust, i, sep = "")) :
argument "value" is missing, with no default
My output should look like
final_val1 <- 800
final_val2 <- 800
And for those values final_val1,final_val2 I should be creating dataframe dynamicaly
Can anybody please help me on this

Answer 1

If we need to use assign, get the object names from the global environment with ls by specifying the pattern 'df' followed by one or more numbers (\\d+), create another vector of 'final_val's ('nm1'), loop through the sequence of 'nm1', assign each of the element in 'nm2' to the value we got from extracting the column 'd' of each 'df's multiplied by 100 and taking its sum.
nm1 <- ls(pattern = "df\\d+")
nm2 <- paste0("final_val", seq_along(nm1))
for(i in seq_along(nm1)){
assign(nm2[i], sum(get(nm1[i])$d*100))
}
final_val1
#[1] 800
final_val2
#[1] 800
Otherwise, we place the datasets in a list, extract the 'd' column, multiply with 100 and do the column sums
unname(colSums(sapply(mget(nm1), `[[`, 'd') * 100))
#800 800
data
df1 <- structure(list(a = c(1L, 1L), b = c(2L, 2L), c = c(3L, 3L), d = c(4L,
4L)), .Names = c("a", "b", "c", "d"), class = "data.frame", row.names = c(NA,
-2L))
df2 <- structure(list(a = c(1L, 1L), b = c(2L, 2L), c = c(3L, 3L), d = c(4L,
4L)), .Names = c("a", "b", "c", "d"), class = "data.frame", row.names = c(NA,
-2L))