try to create new variable using loop in R,but failed

Question

I am a new user to R.I have already imported all data from all my txt file using the code down below,but i want to create a new variable when importing data,the variable is called case.The value of case for the first row is 1 and for the rest is 0.

And when i try to run the code,the console did not say anytime wrong ,the data has been imported, but the new variable wasn't created.I don't know why.

for(i in Filenames){
  perpos <- which(strsplit(i, "")[[1]]==".")
  data=assign(
    gsub(" ","",substr(i, 1, perpos-1)),
    read.table(paste(filepath,i,sep=""),fill=TRUE,header=TRUE,quote ="",row.names = NULL,sep="\t")
  )
  strsplit(i, "")
  filename  = strsplit(as.character(i),"\\.txt")
  data$case = ifelse(data$NAME=="filename",1,0)
}

Don't use data = assign(...); the purpose of assign is not its return value. Your strsplit(i,"") in contrast does need to be assigned somewhere. — Frank
– Frank, Commented Jul 22, 2015 at 16:34
Are you trying to match data$NAME with the variable filename above it or the literal string "filename". — Pierre L
– Pierre L, Commented Jul 22, 2015 at 16:36
not the literal string "filename",data$NAME is a list of names,the first one is case,others are controls.And i forget to deletestrsplit(i,"") — Ran
– Ran, Commented Jul 22, 2015 at 16:45

Ran · Accepted Answer · 2015-07-23 18:39:57Z

1

Thanks guys! I used @joosts's code and made some ajustment. The code down below works just fine.

fn <- paste(filepath,Filenames,sep="")
mylist <- lapply(fn, read.table,fill = TRUE, header = TRUE, quote = "",row.names = NULL, sep = "\t",stringsAsFactors=FALSE)
for(i in 1:length(Filenames)){
mylist[[i]]<- cbind(mylist[[i]], case = 0)
if(nrow(mylist[[i]])>0) {
mylist[[i]]$case[1] <- 1
}
mylist[[i]]<- cbind(mylist[[i]], ID = i)
}
do.call(rbind, mylist)

answered Jul 23, 2015 at 18:39

Ran

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Comments

joosts · Accepted Answer · 2015-07-22 17:44:58Z

0

I am assuming you want to read in multiple text files, with each file containing the same columns (in the same order). In order to combine multiple dataframes (the things that result from calling read.data()), you should call the function rbind(). And I assume your code to get a filename without the extension is slightly overcomplex...

for(file in filenames) {
 sanitized_filename <- gsub(" ", "", strsplit(file, "\\.")[[1]][1])
 file.frame <- read.table(paste(filepath, file, sep=""), fill = TRUE, header = TRUE, quote = "", row.names = NULL, sep = "\t")
 file.frame <- cbind(file.frame, name = I(sanitized_filename), case = 0)
 if(nrow(file.frame)>0) {
   file.frame$case[1] <- 1
 }
 data <- ifelse(exists("data"), rbind(data, file.frame), file.frame)
}

edited Jul 22, 2015 at 17:44

answered Jul 22, 2015 at 17:09

joosts

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10 Comments

Ran Over a year ago

joosts,thanks a lot! But when i try to run the code ,it saysError in rep(xi, length.out = nvar) : attempt to replicate an object of type 'closure',why?

joosts Over a year ago

Not really sure... if you could show me some of data files I could improve the code above... (missing any input I just had to make this one up without testing).

Ran Over a year ago

i'm sorry i can't show you my file,it's data collected from patients. what do you mean by` ifelse(exists("data"), rbind(data, file.frame), file.frame) }`,data wasn't defined before

joosts Over a year ago

Exactly if data didnt exist it is created from the new data frame else it is merged with the existing fast using rbind... I probably will be able to help you with two fake data files as well.

Ran Over a year ago

how can i send you the file? btw,i can't read in all the files using your code,only the first one,and the amount of variables became strange....

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