Append data frames together in a for loop

Question

I have a for loop which produces a data frame after each iteration  I want to append all data frames together but finding it difficult  Following is what I  am trying  please suggest how to fix it   d   NULL for  i in 1 7         vector output   model  lt -  some processing      add vector to a dataframe   df  lt - data frame model      df total  lt - rbind d df

User · Answer

In the Coursera course  an Introduction to R Programming  this skill was tested   They gave all the students 332 separate csv files and asked them to programmatically combined several of the files to calculate the mean value of the pollutant   This was my solution       create your empty dataframe so you can append to it    combined df  lt - data frame Date as Date character                         Sulfate double                        Nitrate double                        ID integer        for loop for the range of documents to combine   for i in min id   max id           using sprintf to add on leading zeros as the file names had leading zeros     read  lt - read csv paste getwd       directory      sprintf   03d   i    csv   sep            in your loop  add the files that you read to the combined df     combined df  lt - rbind combined df  read

User · Answer

You should try this   df total   data frame   for  i in 1 7         vector output     model  lt -  some processing        add vector to a dataframe     df  lt - data frame model      df total  lt - rbind df total df

User · Answer

Try to use rbindlist approach over rbind as it s very  very fast   Example   library data table         example 1  slow processing         table 1  lt - data frame x   NA  y   NA  time taken  lt - 0 for  i in 1 100      start time   Sys time     x  lt - rnorm 100    y  lt - x 2  x 3   z  lt - cbind data frame x   x  y   y     table 1  lt - rbind table 1  z    end time  lt - Sys time     time taken   lt -  end time - start time    time taken    print time taken   gt  Time difference of 0 1637917 secs      example 2  faster processing        table 2  lt - list   t0  lt - 0 for  i in 1 100      s0   Sys time     x  lt - rnorm 100    y  lt - x 2   x 3    z  lt - cbind data frame x   x  y   y     table 2  i    lt - z    e0  lt - Sys time     t0   lt -  e0 - s0    t0    s1   Sys time   table 3  lt - rbindlist table 2  e1   Sys time    t1   lt -  e1-s1    t0 t1  gt  Time difference of 0 03064394 secs

User · Answer

x  lt - c 1 10      empty data frame with variables ----  df  lt - data frame x1 character                         y1 character     for  i in x      a1  lt - c x1    paste0  The number is   x i   y1    paste0  This is another number    x i      df  lt - rbind df a1     names df   lt - c  st column   nd column   View df    that might be a good way to do so

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For me  it worked very simply  At first  I made an empty data frame  then in each iteration I added one column to it  Here is my code  df  lt - data frame modelForOneIteration  for i in 1 10     model  lt -   some processing   df  i    model

User · Answer

Don t do it inside the loop  Make a list  then combine them outside the loop   datalist   list    for  i in 1 5              make some data     dat  lt - data frame x   rnorm 10   y   runif 10       dat i  lt - i    maybe you want to keep track of which iteration produced it      datalist  i    lt - dat   add it to your list    big data   do call rbind  datalist    or big data  lt - dplyr  bind rows datalist    or big data  lt - data table  rbindlist datalist    This is a much more R-like way to do things  It can also be substantially faster  especially if you use dplyr  bind rows or data table  rbindlist for the final combining of data frames

User · Answer

Again maRtin is correct but for this to work you have start with a dataframe that already has at least one column  model  lt -  some processing df  lt - data frame col1 model   for  i in 2 17         model  lt -   some processing      nextcol  lt -  data frame model       colnames nextcol   lt - c paste  col   i  sep        rename the comlum      df  lt - cbind df  nextcol

User · Answer

Here are some tidyverse and custom function options that might work depending on your needs   library tidyverse     custom function to generate  filter  and mutate the data  combine dfs  lt - function i    data frame x   rnorm 5   y   runif 5     gt        filter x  lt  y    gt        mutate x plus y   x   y    gt        mutate i   i     df  lt - 1 5   gt   map df  combine dfs     df  lt - map df 1 5   combine dfs       both give the same results  gt  df   gt   head     A tibble  6 x 4        x      y x plus y     i     lt dbl gt    lt dbl gt      lt dbl gt   lt int gt  1 -0 973 0 673    -0 300     1 2 -0 553 0 0463   -0 507     1 3  0 250 0 716     0 967     2 4 -0 745 0 0640   -0 681     2 5 -0 736 0 228    -0 508     2 6 -0 365 0 496     0 131     3   You could do something similar if you had a directory of files that needed to be combined   dir path  lt -   path to data test directory   list files dir path   combine files  lt - function path  file     read csv paste0 path  file     gt        filter a  lt  b    gt        mutate a plus b   a   b    gt        mutate file name   file      df  lt - list files dir path      csv      gt      map df  combine files dir path         or if you have Excel files  using the readxl package  combine xl files  lt - function path  file     readxl  read xlsx paste0 path  file     gt        filter a  lt  b    gt        mutate a plus b   a   b    gt        mutate file name   file      df  lt - list files dir path      xlsx      gt      map df  combine xl files dir path

[r] Append data frames together in a for loop

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