in case you are interested in reading some data from a .txt file and only extract few columns of that file into a new .txt file with a customized header, the following code might be useful:
# input some data from 2 different .txt files:
civit_gps <- read.csv(file="/path2/gpsFile.csv",head=TRUE,sep=",")
civit_cam <- read.csv(file="/path2/cameraFile.txt",head=TRUE,sep=",")
# assign the name for the output file:
seqName <- "seq1_data.txt"
#=========================================================
# Extract data from imported files
#=========================================================
# From Camera:
frame_idx <- civit_cam$X.frame
qx <- civit_cam$q.x.rad.
qy <- civit_cam$q.y.rad.
qz <- civit_cam$q.z.rad.
qw <- civit_cam$q.w
# From GPS:
gpsT <- civit_gps$X.gpsTime.sec.
latitude <- civit_gps$Latitude.deg.
longitude <- civit_gps$Longitude.deg.
altitude <- civit_gps$H.Ell.m.
heading <- civit_gps$Heading.deg.
pitch <- civit_gps$pitch.deg.
roll <- civit_gps$roll.deg.
gpsTime_corr <- civit_gps[frame_idx,1]
#=========================================================
# Export new data into the output txt file
#=========================================================
myData <- data.frame(c(gpsTime_corr),
c(frame_idx),
c(qx),
c(qy),
c(qz),
c(qw))
# Write :
cat("#GPSTime,frameIdx,qx,qy,qz,qw\n", file=seqName)
write.table(myData, file = seqName,row.names=FALSE,col.names=FALSE,append=TRUE,sep = ",")
Of course, you should modify this sample script based on your own application.