Appending to a text file in a loop - r

Question

I have a data frame called MetricsInput which looks like this:
ID ExtractName Dimensions Metrics First_Ind
124 extract1.txt ga:date gs:sessions 1
128 extract1.txt ga:date gs:sessions 0
134 extract1.txt ga:date gs:sessions 0
124 extract2.txt ga:browser ga:users 1
128 extract2.txt ga:browser ga:users 0
134 extract2.txt ga:browser ga:users 0
I'm trying to use the above data frame in a loop to run a series of queries, which ultimately will create 2 text files, extract1.txt and extract2.txt. The reason I have the first_ind field is I only want to append the column headings on the first run through each unique file.
Here's my loop -- the issue I'm having is that the data for each ID is not appending -- I seem to be overwriting my results, not appending. Where did I go wrong?
for(i in seq(from=1, to=nrow(MetricsInput), by=1)){
id <- MetricsInput[i,1]
myresults <- ga$getData(id,batch = TRUE, start.date="2013-12-01", end.date="2014-01-01", metrics = MetricsInput[i,4], dimensions = MetricsInput[i,3])
appendcolheads <- ifelse(MetricsInput[i,5]==1, TRUE, FALSE)
write.table(myresults, file=MetricsInput$ExtractName[i], append=TRUE, row.names = FALSE, col.names = appendcolheads, sep="\t")
}

Answer 1

Although you can get this code to work, it doesn't look like the right approach at all. As #MrFlick said in the comments it's very hard to help without being able to reproduce your problem, but I would do something along the following lines
GetData <- function(id, metric, dim) {
d <- ga$getData(id, batch = TRUE, start.date="2013-12-01",
end.date="2014-01-01", metrics = metric, dimensions = dim)
d$id <- id
d
}
myresults <- Map(GetData,
id = MetricsInput$ID,
metric = MetricsInput$Metrics,
dim = MetricsInput$Dimensions)
This will give you a list whose ith component is the output of the ith iteration in your for loop. So now you have to split it in two to write it in the files you wanted
myresultslist <- split(myresults, MetricsInput$ExtractName)
myresultslist <- lapply(myresultslist, do.call, what = rbind)
Map(write.table, x = myresultslist, file = names(myresultslist),
row.names = FALSE, sep = "\t")

Answer 2

Why don't you create a data frame in the loop and then write it to the text file?
myresults <- data.frame()
for (i in yourloop) {
#your code here
id <- MetricsInput[i,1]
temp <- ga$getData(id,batch = TRUE, start.date="2013-12-01", end.date="2014-01-01", metrics = MetricsInput[i,4], dimensions = MetricsInput[i,3])
myresults <- rbind(myresults, temp)
}
write.csv(myresults, ...)