how to write multiple dataframe to a single csv file in a loop in R?

Question

I would like to write a multiple dataframe "neighbours_dataframe" in a single CSV file :

I use this line to write the multiple dataframe to multiple file :

for(i in 1:vcount(karate)){
write.csv(neighbours_dataframe[[i]], file = as.character(V(karate3)$name[i]),row.names=FALSE)}

if I use this code:

for(i in 1:vcount(karate)){
write.csv(neighbours_dataframe[[i]], file = "karate3.csv",row.names=FALSE)}

this would give me just the last dataframe in the csv file :

I was wondering , How could I have a single CSV file which have all the dataframe in the way that the column header of the first dataframe just written to the csv file and all other data frame copied in a consecutive manner ?

thank you in advance

If all data.frames have the same set of column names, try do.call(rbind, neighbours_dataframe) (assuming neighbours_dataframe is a list of data.frames), then write the result of that to a csv. If they don't all share the same columns, then try dplyr::rbind_all(neighbours_dataframe). — jbaums
– jbaums, Commented Nov 17, 2014 at 7:47
@Neal append won't work for write.csv - see my comment below. — jbaums
– jbaums, Commented Nov 17, 2014 at 8:50
thak you @Neal as jbaums said append didn't work and I get the warnings and also it was just like the second line code nothing happened — f.a
– f.a, Commented Nov 17, 2014 at 11:15

Richie Cotton · Accepted Answer · 2014-11-17 09:34:11Z

2

Two methods; the first is likely to be a little faster if neighbours_dataframe is a long list (though I haven't tested this).

Method 1: Convert the list of data frames to a single data frame first

As suggested by jbaums.

library(dplyr)
neighbours_dataframe_all <- rbind_all(neighbours_dataframe)
write.csv(neighbours_dataframe_all, "karate3.csv", row.names = FALSE)

Method 2: use a loop, appending

As suggested by Neal Fultz.

for(i in seq_along(neighbours_dataframe))
{
  write.table(
    neighbours_dataframe[[i]], 
    "karate3.csv", 
    append    = i > 1, 
    sep       = ",", 
    row.names = FALSE,
    col.names = i == 1
  )
}

edited Nov 17, 2014 at 9:34

answered Nov 17, 2014 at 8:16

Richie Cotton

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4 Comments

jbaums Over a year ago

append isn't possible for write.csv. See ?write.table, which states, for CSV files, "These wrappers are deliberately inflexible: they are designed to ensure that the correct conventions are used to write a valid file. Attempts to change append, col.names, sep, dec or qmethod are ignored, with a warning.". Instead, you might have to do something like: write.table(neighbours_dataframe[[i]], "karate3.csv", append = i > 1, row.names = FALSE, col.names = i==1, sep=',') (within your for loop).

Richie Cotton Over a year ago

@jbaums Good spot; fixed.

jbaums Over a year ago

I think you do need to suppress row names as well, though, otherwise column names aren't correctly aligned. See

L <- data.frame(a=1:3, b=1:3); L <- list(d, d); f <- tempfile(fileext='.csv'); for(i in seq_along(L)) write.table(L[[i]], f, append=i>1, sep=",", col.names=i==1); file.show(f)

.

f.a Over a year ago

thank you @RichieCotton, the first method just work perfectly fine on rather long list

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