HI All, I have a data frame such as:> testx y p d [1,] 1 0 10 21 0 [2,] 2 3 11 12 0 [3,] 3 4 12 23 0 [4,] 3 5 13 24 0 and I want to perfor some operations on the first two coulums, conditional on the uneqaulity values on the 3rd and 4th columns. For instance: j = 3 test[test[,1] == j, 5] = test[test[,1] == j,2] + test[test[,2] == j,1] gives me the result: test: x y p d [1,] 1 0 10 21 0 [2,] 2 3 11 12 0 [3,] 3 4 12 23 6 [4,] 3 5 13 24 7 My probblem is the following: I want to perform the operation test[test[,1] == j,2] + test[test[,2] == j,1] only if the value of column p and column d are different at the positions where x or y = j. In practice, I don't want to perform the first operation because test[2,4 is 12 and test[1,3] is 12 as well. I tried an if statement with little success: if(test[test[,1] == j,3] != test[test[,2] == j,4]){ test[test[,1] == j, 5] = test[test[,1] == j,2] + test[test[,2] == j,1] } Warning message: the condition has length > 1 and only the first element will be used in: if (test[test[, 1] == j, 3] != test[test[, 2] == j, 4]) { Could anyone lend some advice? Cheers, Federico -- Federico C. F. Calboli Department of Epidemiology and Public Health Imperial College, St Mary's Campus Norfolk Place, London W2 1PG Tel +44 (0)20 7594 1602 Fax (+44) 020 7594 3193 f.calboli [.a.t] imperial.ac.uk f.calboli [.a.t] gmail.com
Dear Frederico>From your example it is not clear to me what you like to obtain:Please have a look on the slightly changed example here (I changed two values to show a potentially undesired side effect of your coding. test <- data.frame(rbind(c(3,3,10,21,0), c(2,3,11,12,0), c(3,4,12,23,0), c(3,5,13,24,0))) names(test) <- c("x","y","p","d","su") test>> x y p d su >> 1 3 3 10 21 0 >> 2 2 3 11 12 0 >> 3 3 4 12 23 0 >> 4 3 5 13 24 0j <- 3 test[test[,1] == j, 5] <- test[test[,1] == j,2] + test[test[,2] == j,1]>> > > Warning message: >> longer object length >> is not a multiple of shorter object length in: >> test[test[, 1] == j, 2] + test[test[, 2] == j, 1]Your code example produces now a warning for the adapted data frame "test", since one tries to add two vectors of length 2 and 3, respectively. The result is based on recycling of the smaller vector. In your example there was no warning since the second column had only one entry. The result with the adapted data frame is: test>> x y p d su >> 1 3 3 10 21 6 >> 2 2 3 11 12 0 >> 3 3 4 12 23 6 >> 4 3 5 13 24 8Is that kind of recycling desired in your application. Otherwise you should be careful with the coding example above. Regards, Christoph Buser -------------------------------------------------------------- Christoph Buser <buser at stat.math.ethz.ch> Seminar fuer Statistik, LEO C13 ETH (Federal Inst. Technology) 8092 Zurich SWITZERLAND phone: x-41-44-632-4673 fax: 632-1228 http://stat.ethz.ch/~buser/ -------------------------------------------------------------- Federico Calboli writes: > HI All, > > I have a data frame such as: > > > test > x y p d > [1,] 1 0 10 21 0 > [2,] 2 3 11 12 0 > [3,] 3 4 12 23 0 > [4,] 3 5 13 24 0 > > > and I want to perfor some operations on the first two coulums, > conditional on the uneqaulity values on the 3rd and 4th columns. > > For instance: > > j = 3 > test[test[,1] == j, 5] = test[test[,1] == j,2] + test[test[,2] == j,1] > > gives me the result: > > test: > > x y p d > [1,] 1 0 10 21 0 > [2,] 2 3 11 12 0 > [3,] 3 4 12 23 6 > [4,] 3 5 13 24 7 > > > My probblem is the following: I want to perform the operation > test[test[,1] == j,2] + test[test[,2] == j,1] only if the value of > column p and column d are different at the positions where x or y = j. > In practice, I don't want to perform the first operation because > test[2,4 is 12 and test[1,3] is 12 as well. > > I tried an if statement with little success: > > if(test[test[,1] == j,3] != test[test[,2] == j,4]){ > test[test[,1] == j, 5] = test[test[,1] == j,2] + test[test[,2] == j,1] > } > Warning message: > the condition has length > 1 and only the first element will be used in: > if (test[test[, 1] == j, 3] != test[test[, 2] == j, 4]) { > > Could anyone lend some advice? > > Cheers, > > Federico > -- > Federico C. F. Calboli > Department of Epidemiology and Public Health > Imperial College, St Mary's Campus > Norfolk Place, London W2 1PG > > Tel +44 (0)20 7594 1602 Fax (+44) 020 7594 3193 > > f.calboli [.a.t] imperial.ac.uk > f.calboli [.a.t] gmail.com > > ______________________________________________ > R-help at 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
Hi try ifelse() but I you probably shall put your problem clearer. HTH Petr On 8 Feb 2006 at 18:12, Federico Calboli wrote: From: Federico Calboli <f.calboli at imperial.ac.uk> To: r-help <r-help at stat.math.ethz.ch> Organization: Imperial College London Date sent: Wed, 08 Feb 2006 18:12:37 +0000 Subject: [R] logical condition in vector operation Send reply to: f.calboli at imperial.ac.uk <mailto:r-help-request at stat.math.ethz.ch?subject=unsubscribe> <mailto:r-help-request at stat.math.ethz.ch?subject=subscribe>> HI All, > > I have a data frame such as: > > > test > x y p d > [1,] 1 0 10 21 0 > [2,] 2 3 11 12 0 > [3,] 3 4 12 23 0 > [4,] 3 5 13 24 0 > > > and I want to perfor some operations on the first two coulums, > conditional on the uneqaulity values on the 3rd and 4th columns. > > For instance: > > j = 3 > test[test[,1] == j, 5] = test[test[,1] == j,2] + test[test[,2] == j,1] > > gives me the result: > > test: > > x y p d > [1,] 1 0 10 21 0 > [2,] 2 3 11 12 0 > [3,] 3 4 12 23 6 > [4,] 3 5 13 24 7 > > > My probblem is the following: I want to perform the operation > test[test[,1] == j,2] + test[test[,2] == j,1] only if the value of > column p and column d are different at the positions where x or y = j. > In practice, I don't want to perform the first operation because > test[2,4 is 12 and test[1,3] is 12 as well. > > I tried an if statement with little success: > > if(test[test[,1] == j,3] != test[test[,2] == j,4]){ > test[test[,1] == j, 5] = test[test[,1] == j,2] + test[test[,2] == j,1] > } Warning message: the condition has length > 1 and only the first > element will be used in: if (test[test[, 1] == j, 3] != test[test[, 2] > == j, 4]) { > > Could anyone lend some advice? > > Cheers, > > Federico > -- > Federico C. F. Calboli > Department of Epidemiology and Public Health > Imperial College, St Mary's Campus > Norfolk Place, London W2 1PG > > Tel +44 (0)20 7594 1602 Fax (+44) 020 7594 3193 > > f.calboli [.a.t] imperial.ac.uk > f.calboli [.a.t] gmail.com > > ______________________________________________ > R-help at 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.htmlPetr Pikal petr.pikal at precheza.cz