Dynamically create CSV file from other CSV files in R

Question

Let's say I have a set of CSV files in a folder called "my data" which is a folder in my working directory. The CSV files are matrices and looking something like:

> a
     [,1] [,2] [,3] [,4]
[1,]    3    3    3    3
[2,]    3    3    3    3
[3,]    3    3    3    3
[4,]    3    3    3    3
> b
     [,1] [,2] [,3] [,4]
[1,]    1    1    1    1
[2,]    2    2    2    2
[3,]    1    1    1    1
[4,]    2    2    2    2
> c
     [,1] [,2] [,3] [,4]
[1,]    3    3    3    3
[2,]    9    9    9    9
[3,]    3    3    3    3
[4,]    9    9    9    9

Let's say I have another folder in my working directory called "my results." In it I want to create another CSV file (call it "my_results") that has the results of the analyses performed on the CSV files in "my data." For example if I calculated the mean and standard deviation of a, b, and c "my_results" would look like:

> my_results
  mean   sd
a  3.0 0.00
b  1.5 0.52
c  6.0 3.10

The idea being every row of the new CSV would correspond to one of the CSVs in "my data" and the columns of the new CSV would correspond to a particular analysis run. Thank you.

setwd("mydata"); out <- do.call("rbind", lapply(dir(), function(x) dosomething(data = read.csv(x)))); write.csv(out, file = "../myresults/my_results.csv"); setwd("..") — Thomas

MarkusN MarkusN · Accepted Answer · 2015-08-28T15:31:57

lapply is your friend:

my_data = lapply(list.files("my data", "*.csv"), read.csv)
my_result = lapply(my_data, your_fun())
write.csv(dplyr::bind_rows(my_result), "my data/my results.csv")

you get the convienient bind_rows function with package dplyr

Dynamically create CSV file from other CSV files in R

1 Answers