Create and fill a list with duplicates of a data frame in R?

Question

I'm building a naive Bayes classifier in R, a language I am not familiar with.

I've got multiple csv files for testing the trained classifier, which become data frames when read into R. There are 20 possible categories a given document can be classified into, and each test file contains many documents, so I need an array of 20 copies of a test file to calculate the probabilities for the 20 categories and choose the best one for each document in that test file.

So once I've read a csv file into R and have a data frame, how do I create an array or list with 20 copies of this data frame?

This is confusing. Why do you want an object containing 20 copies of the same data frame? I'm struggling to think of any situation in which this would be necessary. — inhuretnakht, Jun 02 '15 at 22:51
Nicely solved here: http://stackoverflow.com/questions/8753531/repeat-data-frame-n-times — vikjam, Jun 02 '15 at 23:05

score 2 · Answer 1 · answered Jun 02 '15 at 22:58

df <- read.csv(text='a,b\n1,a\n2,b\n3,c\n');
df;
##   a b
## 1 1 a
## 2 2 b
## 3 3 c
rep(list(df),20);
## [[1]]
##   a b
## 1 1 a
## 2 2 b
## 3 3 c
##
## [[2]]
##   a b
## 1 1 a
## 2 2 b
## 3 3 c
##
## ... (snip) ...
##
## [[19]]
##   a b
## 1 1 a
## 2 2 b
## 3 3 c
##
## [[20]]
##   a b
## 1 1 a
## 2 2 b
## 3 3 c

Create and fill a list with duplicates of a data frame in R?

1 Answers1