This may be of help dat <- data.frame(dbh = c(30, 29 , 28, 27, 26, 25, 24, 23, 22, 21, 20, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20), form = c( "tree", "tree", "tree", "tree", "tree", "tree", "tree", "tree", "tree", "tree", "tree","liana","liana", "liana","liana","liana","liana","liana","liana","liana", "liana","liana", "palm", "palm", "palm", "palm", "palm", "palm", "palm", "palm", "palm", "palm", "palm")) attach(dat) ans <- ifelse(form == "tree", exp(-4.898+4.512*log(dbh)-0.319*(log(dbh))^2), NA) ans <- ifelse(form == "liana", 10^(0.07 + 2.17 * log10 (dbh)), ans) data.frame(form,ans) Samuel
Paulo Brando <[EMAIL PROTECTED]> wrote: Dear Rs, I have tried to use conditional expressions to calculate biomass for different life forms (trees, lianas, and palms). Here is an example: > lifeform dbh form 1 30 tree 2 29 tree 3 28 tree 4 27 tree 5 26 tree 6 25 tree 7 24 tree 8 23 tree 9 22 tree 10 21 tree 11 20 tree 12 15 liana 13 14 liana 14 13 liana 15 12 liana 16 11 liana 17 10 liana 18 9 liana 19 8 liana 20 7 liana 21 6 liana 22 5 liana 23 30 palm 24 29 palm 25 28 palm 26 27 palm 27 26 palm 28 25 palm 29 24 palm 30 23 palm 31 22 palm 32 21 palm 33 20 palm ### I want to include biomass lifeform$biomass <- { if(lifeform$form=="tree") exp(-4.898+4.512*log(dbh)-0.319*(log(dbh))^2) else{ if (lifeform$form=="liana") 10^(0.07 + 2.17 * log10 (dbh)) else ("NA") } Warning message: the condition has length > 1 and only the first element will be used in: if (lifeform$form == "tree") exp(-4.898 + 4.512 * log(dbh) - ### But I always get the message warning message above. I looked for similar examples in R mail list archive, but they did not help a lot. I am quite new to 'R'. Any material that covers this theme? Thank you very much! Paulo PS. Sorry about the last e-mail. I did not change the message title. ________________________________________ Paulo M. Brando Instituto de Pesquisa Ambiental da Amazonia (IPAM) Santarem, PA, Brasil. Av. Rui Barbosa, 136. Fone: + 55 93 522 55 38 www.ipam.org.br E-mail: [EMAIL PROTECTED] ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html --------------------------------- [[alternative HTML version deleted]] ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html