Hi Philip, My fault for assuming that what worked for the sample data would work for the entire data set. If you run the following code:
# read the file into a data frame phdf<-read.csv("phdf.csv",stringsAsFactors=FALSE) print(dim(phdf)) # create a logical variable for the subsetting step keep<-rep(TRUE,length(phdf$Speed)) # this follows the conventional for(i in ...) syntax # mini (minute index) is the name of the variable # that is assigned the successive values of the # unique values in the Minute column of phdf # here I was lazy and only dealt with the sample data # what I should have done was to create a column # with minute values that don't repeat phdf$hourmin<-phdf$Hour.Z * 60 + phdf$Minute for(mini in unique(phdf$hourmin)) { # mark all minutes that are all zeros for deletion if(all(phdf$Speed[phdf$hourmin == mini] == 0)) keep[phdf$hourmin == mini]<-FALSE # but now there is another condition # that I didn't notice (more laziness) # drop minutes containing ten consecutive zeros # I'll use a cheap trick for this # if the length of the run length encoding (rle) # of the Speed == 0 condition is less than three, # then there can't be a broken run of zeros if(length(rle(phdf$Speed[phdf$hourmin == mini])$length)<3) keep[phdf$hourmin == mini]<-FALSE } # now drop any rows for which has marked FALSE (note all caps!) phdf<-phdf[keep,] print(dim(phdf)) You will see that it has removed 67 rows. This is the same as if I had only applied the first "all zeros" condition, for there were no unique minutes with 11 observations that contained a single non-zero speed value. I can see that you are getting short runs of zero speeds near the end. I assume that this is due to the balloon slowly bumping along the ground. Often just looking at the data can suggest solutions to problems like this. Coincidentally I am about to email an old friend of mine whose sons have dabbled in sending balloons high into the air and I will let them know that they are not alone in performing this unusual practice. If I haven't answered all your questions, feel free to let me know. Jim On Sun, Aug 16, 2020 at 4:39 AM Philip <herd_...@cox.net> wrote: > > Thanks for getting back to me so quickly. > > I can get your code to run without errors but I'm not sure what it > accomplishes since I still get 813 rows of data and 11 variables. The > entire file for a January flight is attached. Also attached is a .jpg of a > flight from a couple of years ago where my wife putzed back and forth across > a road for over an hour by going up or down to catch different winds. Stuff > like this is one of the charms of the sport for those of us who are easily > amused. > > keep <- rep(TRUE,length(phdf$Speed)) #813 repetitions of TRUE > for(mini in unique(phdf$Minute)) > if(all(phdf$Speed[phdf$Minute==mini]==0)) > keep[phdf$Minute==mini]<-False #813 repetitions of > TRUE in the keep data file. > > #Don't understand the assignment (<-) to FALSE > phdf <- phdf[keep,] #Still have 813 rows of data. > > As you may know, we lay out the balloon and then blow cold air into the > envelope with a gas powered fan. When it is packed we "go hot". Just > before we turn on the pilot light and hit the burner we will turn on the > tracking software which results in several minutes of no movement at the > beginning of the flight. This is what is happening between rows 2 and 70 of > the attached spreadsheet. You will also notice that the balloon slowly > accelerates between rows 71 and 79 p to about 3.4 MPH just after liftoff. > The no movement is what I want to eliminate. > > Can you let me know what I am missing. > > Two more thing. I really not sure about the: > > for(mini in unique(phdf$Minute)) > > .....line of code. I understand the unique function but not the "mini > in..." part. Is mini a function or just a label? I understand stuff like: > > for(i in 1:5) print(1:i) > > .....from the R base documentation but not real sure how it fits in here. > > And finally, I'm retired, So I have plenty of time and determined to learn > R. But I keep running into things like the "mini in unique" command. I > have read four or five books and watched or read dozens of tutorials but > there always seems to be another layer that alludes me. Any suggestions? > > Philip ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.