Hi, Your description isn't clear:
On Thursday, July 24, 2014, Matthew <mccorm...@molbio.mgh.harvard.edu> wrote: > I am coming from the perspective of Excel and VBA scripts, but I would > like to do the following in R. > > I have a data frame with 14 columns and 32,795 rows. > > I want to check the value in column 8 (row 1) to see if it is a 0. > If it is not a zero, proceed to the next row and check the value for > column 8. > If it is a zero, then > a) change the zero to a 1, > b) divide the value in column 9 (row 1) by 1, Row 1, or the row in which column 8 == 0? Why do you want to divide by 1? > c) place the result in column 10 (row 1) and Ditto on the row 1 question. What do you want column 10 to be if column 8 isn't 0? Does it already have a value. I suppose it must. > d) repeat this for each of the other 32,794 rows. > > Is this possible with an R script, and is this the way to go about it. If > it is, could anyone get me started ? Assuming you want to put the new values in the rows where column 8 == 0, you can do it in two steps: mydata[,10] <- ifelse(mydata[,8] == 0, mydata[,9]/whatever, mydata[,10]) #where whatever is the thing you want to divide by that probably isn't 1 mydata[,8] <- ifelse(mydata[,8] == 0, 1, mydata[,8]) R programming is best done by thinking about vectorizing things, rather than doing them in loops. Reading the Intro to R that comes with your installation is a good place to start. Sarah > > Matthew > > > -- Sarah Goslee http://www.stringpage.com http://www.sarahgoslee.com http://www.functionaldiversity.org [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org 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.
