On Mon, Jan 17, 2011 at 3:51 PM, michael.hopgood <[email protected]> wrote: > > Dear R family, > I am a relative newbie and have been dabbling with R for a little while. > Simple things really, but my employers are beginning to see the benefits of > using R instead of excel. We have a remote monitoring station measuring > groundwater levels. We download the date as a .csv file and up until now, > we have been using excel to analyse the data. It’s been a hassle trying to > wrestle with that damn program as my boss wants to do things that excel was > never meant to do, so I’ve convinced my boss to give R a chance. It’s been > a steep learning curve, but I’m fairly confident I can reduce the amount of > labour involved in producing and improving the graphs we show our clients. > > The groundwater levels are measured by pressure sensors lowered into the > monitoring wells. After a certain time, the sensors were lowered further > into the well, thus creating a disparity in the measurements. > > The data frame I import into R looks something like this: > Date Waterhead (mm) > 10-01-01 100 > 10-01-02 105 > 10-01-03 101 > 10-01-04 99 > 10-01-05 85 > 10-01-06 200 > 10-01-07 199 > 10-01-08 195 > 10-01-09 185 > 10-01-10 170 > > For example, on the 10-10-06, the sensor was lowered by 115 mm. > When I download the csv file, I download the data from the beginning of the > measurement period. I then need to adjust the height by 115 mm to account > for the lowering of the parameter. My question to you is how do I do that > in R? > I am after a formula or a manipulation that selects the first five > measurements and adds a fixed amount. This is something that is added > everytime I download the csv file and import it into R so that when I > display my data, it is based on the following data frame: > > Date Waterhead (mm) > 10-01-01 215 > 10-01-02 220 > 10-01-03 216 > 10-01-04 214 > 10-01-05 200 > 10-01-06 200 > 10-01-07 199 > 10-01-08 195 > 10-01-09 185 > 10-01-10 170 > > In short, I want to select a fixed number of rows of a column from my data > frame, add a constant to these, and insert the new values into their > respective rows without affecting the subsequent rows. I hope I have > produced a reproducible example. I have been searching high and low for a > solution, but have come up against a brick wall. I feel I have read > something that tackles this some time in the past, but can’t find it again. > Thanks in advance!
Try this using the builtin data frame, BOD: > BOD Time demand 1 1 8.3 2 2 10.3 3 3 19.0 4 4 16.0 5 5 15.6 6 7 19.8 > > # add 100 to the first two rows in column 2 > BOD[1:2, 2] <- BOD[1:2, 2] + 100 > BOD Time demand 1 1 108.3 2 2 110.3 3 3 19.0 4 4 16.0 5 5 15.6 6 7 19.8 -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com ______________________________________________ [email protected] mailing list 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.
