Running a function multiple times in R

Question

I have 100 data set in *.csv format with the same name but different indexes: myarray1, myarray2,..., myarray100. I have written a function to read these data sets and do some stuff but I don't want to run the function 100 times. This is the main part of function:

 Myfunc <- function(file){
 setwd("C:\\Users\\Desktop\\mydaya")
 data.temp1 <- read.csv("C:\\Users\\Desktop\\mydata\\myarray1.csv",header=FALSE)
 .......
 #core of function
 .....
 }

is it possible to write a for-loop somehow that runs the function itself 100 times and also change the index of "myarray..." in third command line inside the function at the same time: for example myarray1 in

  data.temp <- read.csv("C:\\Users\\Desktop\\mydata\\myarray1.csv",header=FALSE)

becomes myarray2 in second run of the function and so on up to 100 times.

yes but what do you want data.temp to look like after loading 100 files? — AwokeKnowing, Oct 23 '13 at 00:04
see this answer http://stackoverflow.com/questions/2098368/how-do-i-concatenate-a-vector-of-strings-character-in-r you can use a string concatenation in your for loop — pyCthon, Oct 23 '13 at 00:04
@ Awokeknowing; Good question. Actually I correct it here. It should be data.temp+index and it changes each time when myarray changes. So at the end of the day I have 100 data.temp with the same name but different indices. data.temp1, data.temp2,...,data.temp100. — SaZa, Oct 23 '13 at 00:11

score 5 · Accepted Answer · answered Oct 23 '13 at 00:20

5

Are you sure you didn't mean read.csv(file, header=FALSE) ?

Then you just can do

lapply(paste0("myarray", 1:100, ".csv"), Myfunc)

answered Oct 23 '13 at 00:20

Neal Fultz

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@ Neal Fultz; I used laply but I got this error message: Error in match.fun(FUN) : object 'myfunc' not found – SaZa Oct 23 '13 at 17:12
R is case-sensitive; you need to match the capitalization between where you define your function and where you use it in `lapply()`. – Neal Fultz Oct 23 '13 at 17:19
yes I know. can you think of anything else that creates the error? – SaZa Oct 23 '13 at 17:28
R isn't finding your function; run `ls()` and make sure it is there. – Neal Fultz Oct 23 '13 at 19:58

score 1 · Answer 2 · answered Oct 23 '13 at 01:15

1

I think it's not a good idea to use variable names like that. You will be much better of storing the data in the list. I would suggest following methodology

setwd("C:\\Users\\Desktop\\mydata")
files <- dir(pattern = 'myarray.*\\.csv')

dataList <- lapply(files, FUN = Myfunc )

you can then refer to various dataframes by using dataList[[1]] , dataList[[2]] etc. It's much easer to work with list than variables list data.temp1, data.temp2 and so on.

answered Oct 23 '13 at 01:15

CHP

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@ geektrader; I used laply but I got this error message: Error in match.fun(FUN) : object 'myfunc' not found – SaZa Oct 23 '13 at 17:12

Running a function multiple times in R

2 Answers2