CODEWITHSUNDEEP
rdataframe
ndem763
ndem763

Reputation: 352

Creating new dataframes from rows of dataframes in list

I have a large list of dataframes in R that need to be rearranged. I'd like a new list of dataframes where the rows of the nth dataframe are comprised of the nth row of each dataframe in my current list. Here's the setup for a reproducible example:

# Generate example data

df1 = data.frame(x = c(1.3, 2.7, 3.4, 4.1), 
                 y = c(5.6, 6.3, 7.9, 8.5),
                 z = c(10, 9, 13, 12))

df2 = data.frame(x = c(1.3, 2.7, 3.4, 4.1),
                 y = c(5.6, 6.3, 7.9, 8.5),
                 z = c(13, 13, 8, 14))

# As a list:
current_df_list = list(df1, df2)

What I want to create, given current_df_list:

# 1st row of df1, df2 become rows of new_df1
new_df1 = data.frame(x = c(1.3, 1.3), y = c(5.6, 5.6), z = c(10, 13)) 

# 2nd row of df1, df2 become rows of new_df2 
new_df2 = data.frame(x = c(2.7, 2.7), y = c(6.3, 6.3), z = c(9, 13))   

# 3rd row of df1, df2 become rows of new_df3
new_df3 = data.frame(x = c(3.4, 3.4), y = c(7.9, 7.9), z = c(13, 8))   

# 4th row of df1, df2 become rows of new_df4
new_df4 = data.frame(x = c(4.1, 4.1), y = c(8.5, 8.5), z = c(12, 14))  


# Final list I want:
new_df_list = list(new_df1, new_df2, new_df3, new_df4)

I've come up with the following:

# My attempt

new_df_1 = rbind.data.frame(df1[1,], df2[1,])
new_df_2 = rbind.data.frame(df1[2,], df2[2,])
new_df_3 = rbind.data.frame(df1[3,], df2[3,])
new_df_4 = rbind.data.frame(df1[4,], df2[4,])

new_df_list = list(new_df1, new_df2, new_df3, new_df4)

This gives the desired result, but I'm not sure how I can generalize it so it can be performed on a couple hundred data frames and I'm sure there's a more efficient way to do it. Further, what I gave in my attempt doesn't account for the fact that all my current dataframes are contained in a list (I was thinking of using lapply somehow for this aspect).

Upvotes: 1

Views: 79

Answers (1)

akrun
akrun

Reputation: 887851

One option would be to convert to array, use aperm to transpose the array, reconvert it to a list of data.frames. 

ar1 <- array(unlist(current_df_list), c(4,3,2))
ar2 <- aperm(ar1, c(3,2,1))
lapply(seq(dim(ar2)[3]), function(i) 
           setNames(as.data.frame(ar2[,,i]), letters[24:26]))

Upvotes: 1

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