On 03/10/2007 2:23 AM, Chung-hong Chan wrote: > Thanks for your answer. But I have a strange question that I don't > know how to explain and I really don't know how to spot the > problematic part. > > Suppose I have a long list of age, gender and bmi from a data.frame > called msltdata. > >> age <- msltdata$age >> gender <- msltdata$data >> bmi <-msltdata$bmi >> age > [1] 5 10 14 >> gender > [1] 0 0 0 > Levels: 0 1
gender is a factor. The values are stored as indices into the Levels vector, so 0 is stored as 1 and 1 would be stored as 2. Factors commonly arise when you read a dataset from a file, and R thinks one of the columns is a set of character values rather than numbers. To convert gender to a numeric value, you can do this: gender <- as.numeric(as.character(gender)) but I'd recommend avoiding factors in the first place. Duncan Murdoch >> bmi > [1] 17.17693 16.40702 16.87695 >> mapply(bmisds,age,gender,bmi) > > however, when I try to create the vectors once again using the same data, i.e. >> age <- c(5,10,14) >> gender <- c(0,0,0) >> bmi <- c(17.17693,16.40702,16.87695) >> mapply(bmisds,age,gender,bmi) > > This time, I can get the correct calculation. > Would anyone please give me some hints to find out what's went wrong? > > Regards, > C > > > On 10/3/07, Christos Hatzis <[EMAIL PROTECTED]> wrote: >> Instead of >> >>> bmisds(age,gender,bmi) >> Try the vectorized version >> >>> mapply(bmisds, age, gender, bmi) >> See ?mapply >> >> -Christos >> >> >> >>> -----Original Message----- >>> From: [EMAIL PROTECTED] >>> [mailto:[EMAIL PROTECTED] On Behalf Of Chung-hong Chan >>> Sent: Wednesday, October 03, 2007 12:31 AM >>> To: [EMAIL PROTECTED] >>> Subject: [R] How to modify function for list >>> >>> Dear R Gurus, >>> >>> I have a function which calculate the BMI standard deviation >>> score based on the age and gender specific L, M, S value. >>> I have written a function like this >>> >>> bmisds <- function (age, gender, bmi){ >>> if (age ==1 & gender ==1) >>> { >>> bmif <- c(-1.013,16.133,0.07656) >>> } >>> else if (age ==1 & gender ==0) >>> { >>> bmif <- c(-1.79,16.421,0.07149) >>> } >>> else if (age == 2 & gender == 1) >>> { >>> bmif <- c(-1.403,15.58,0.07342) >>> } >>> else if (age == 2 & gender == 0) >>> { >>> bmif <- c(-2.045,15.861,0.07116) >>> } >>> .... >>> >>> (((bmi/bmif[2])**bmif[1] -1)/(bmif[1]*bmif[3])) } >>> >>> This function work when I supply a single variable, e.g. >>> bmisds(1,0,16) >>> >>> When I try it with a list, e.g. >>> age <- c(12,13,14) >>> gender <- c(0,1,1) >>> bmi <- c(14,15,16) >>> bmisds(age,gender,bmi) >>> >>> This function give me wrong answer and error msg. >>> Warning messages: >>> 1: the condition has length > 1 and only the first element >>> will be used in: if (age == 1 & gender == 1) { >>> >>> >>> How can I midify this function to work with list/vector? >>> >>> regards, >>> C >>> >>> >>> -- >>> CH Chan >>> Research Assistant - KWH >>> http://www.macgrass.com >>> >>> ______________________________________________ >>> 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. >>> >>> >> >> > > ______________________________________________ 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.