Dear John, Thank you for your answer. However, it does not make sense to me, as it works only line by line of the data.frame, and I need something for "last observation carried forward" as Peter mentioned. The script does not work as is either, probably due to typos with semi-colons and "if... else" statements, so I cannot really test it.
Best, Ivan -- Dr. Ivan Calandra TraCEr, laboratory for Traceology and Controlled Experiments MONREPOS Archaeological Research Centre and Museum for Human Behavioural Evolution Schloss Monrepos 56567 Neuwied, Germany +49 (0) 2631 9772-243 https://www.researchgate.net/profile/Ivan_Calandra On May 10, 2019 at 3:47 PM John McKown <john.archie.mck...@gmail.com> wrote: > This is my approach. It is based entirely on what you said (multiply by 1000 > to convert from nm to µm, but I think it is divide by). It assumes that the > starting value is in µm. If the starting value is in nm, change the > "factor=1" to "factor=1000". That µm is micro-meters (10^-6) and nm is > nano-meters (10^-9), so divide by would be correct. > > factor=1; > for (i in 1:length(my.data$V19)) { > print("Start");print(factor);print(my.data[i,]); > if (my.data$V19[i] == "nm") { factor=1000; my.data$V19[i]="µm";print("nm");} > else if (my.data$V19[i] == "µm") {factor=1;}; > if (suppressWarnings(! is.na <http://is.na> (as.numeric(my.data$V19[i])))) { > my.data$V19[i] = as.character(as.numeric(my.data$V19[i]) * factor); > print("changed"); } > print(factor);print(my.data[i,]);print("End"); > > > > On Fri, May 10, 2019 at 6:54 AM Ivan Calandra < calan...@rgzm.de > <mailto:calan...@rgzm.de> > wrote: > > > Dear useRs, > > > > Below is a sample of my dataset (I have more rows and columns). > > > > As you can see in the 2nd column, there are values, the name of the > > parameter > > ('Sq' in that case), some integer ('45' in that case) and the unit ('µm' > > or > > 'nm'). > > I know how to extract the rows of interest (those with values), but they > > are > > expressed in different units. All values following a line with the unit > > are > > expressed in that unit, but the number of lines is not constant > > (sometimes each > > value is expressed in a different unit so there will be a new unit line, > > but > > there are sometimes several values in a row expressed in the same unit so > > without unit lines in between). I hope this is clear (it should be with > > the > > example provided). > > This messy dataset comes from an external software so I don't have any > > means to > > format the ways the data are collated. I have to find a way to deal with > > it in > > R. > > > > What I would like to do is convert the values in nm to µm; I just need to > > multiply by 1000. > > > > What I don't know is how to identify the values that are expressed in nm > > (all > > values that follow a line with 'nm' until there is a line with 'µm'). > > > > I don't even know how I should search online because I don't know how > > this kind > > of operation is called. > > Any help is appreciated. > > > > Thank you in advance. > > Ivan > > > > > > my.data <- structure(list(V1 = c("2019/05/10", "#", "#", "#", > > "2019/05/10", > > "2019/05/10", "2019/05/10", "#", "#", "#", "2019/05/10", "#", "#", "#", > > "2019/05/10", "#", "#", "#", "2019/05/10", "2019/05/10"), V19 = > > c("0.2012800083", "45", "Sq", "µm", "0.3634383236", "0.4360454777", > > "0.3767733568", "45", "Sq", "nm", "102.013048", "45", "Sq", "µm", > > "0.1413840498", "45", "Sq", "nm", "65.4459715", "46.45802917")), > > row.names = > > c(NA, 20L), class = "data.frame") > > > > -- > > Dr. Ivan Calandra > > TraCEr, laboratory for Traceology and Controlled Experiments > > MONREPOS Archaeological Research Centre and > > Museum for Human Behavioural Evolution > > Schloss Monrepos > > 56567 Neuwied, Germany > > +49 (0) 2631 9772-243 > > https://www.researchgate.net/profile/Ivan_Calandra > > <https://www.researchgate.net/profile/Ivan_Calandra> > > > > ______________________________________________ > > R-help@r-project.org <mailto:R-help@r-project.org> mailing list -- To > > UNSUBSCRIBE and more, see > > https://stat.ethz.ch/mailman/listinfo/r-help > > <https://stat.ethz.ch/mailman/listinfo/r-help> > > PLEASE do read the posting guide > > http://www.R-project.org/posting-guide.html > > <http://www.R-project.org/posting-guide.html> > > and provide commented, minimal, self-contained, reproducible code. > > > > > -- > This is clearly another case of too many mad scientists, and not enough > hunchbacks. > > > Maranatha! <>< > John McKown > ______________________________________________ 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.