在R中使用write.table写入csv文件时出现不良对齐

Question

I am trying to write and append my output to a csv file using R . First, the program will write the header and then inside a for loop append the generated rows. An example code is as follows:

   writeLines(text=c('Mean','Sd','\n'),'file.csv',sep=',')
   for(i in 1:5)
    {x <- rnorm(10); dat1 <- cbind(mean(x),sd(x))
      write.table(dat1,'file.csv',append=TRUE,sep=',',col.names=FALSE)
    }

But this shifts my first row to right by one element giving the following in csv output. How can I avoid this? Is there another way to achieve what I am trying to do here?

EDIT Also, how do we remove the column labeling which is 1 in this case? col.names=FALSE does not seem to help. I used row.names=FALSE as suggested by @Roman Luštrik. It solved this problem. But the first row shifting problem is not yet to be addressed.

Answer 1

I've often had to write to files in such a manner. I usually do it this way.

If file already exists, just append without the column and row names. If not, create a brand new one.

x <- rnorm(10); dat1 <- data.frame(Mean = mean(x), Sd = sd(x))
if (file.exists("file.csv")) {
   write.table(dat1, file = "file.csv", append = TRUE, col.names = FALSE, row.names = FALSE, sep = ",")
} else {
   write.table(dat1, file = "file.csv", col.names = TRUE, row.names = FALSE, sep = ",")
}

Answer 2

Why not use paste() ?

writeLines(text=paste(c('Mean','Sd'),collapse=','),'file.csv',sep="\n")
for(i in 1:5) {
  x <- rnorm(10); dat1 <- cbind(mean(x),sd(x))
  write.table(dat1, 'file.csv', append=TRUE, sep=',', row.names=FALSE, col.names=FALSE)
}

Answer 3

To understand how the CSV file looks like, I suggest that you open it in a text editor and not in Excel (which transforms it). Because then you could see that your CSV starts like:

Mean,Sd,
,"1",0.441737369447746,1.07695222886305
[...]

...two too many commas.

In your writeLines statement, what you meant is the following:

   writeLines(paste('Mean','Sd',sep=","),'file.csv')

What is wrong in your case is that you replaced the default sep="\\n" of writeLines with sep="," and apparently writeLines prints a separator also after the last item, unlike paste . (This makes much more sense when printing lines as the default operation, closing also the last line with a \\n .)

In write.Table , use row.names=FALSE .