search for: transformbi

I have a question regarding?the very useful doBy package, and specifically, the transformBy() function?with the lag() and diff() functions. ?It is often useful to lag or difference data within a panel, i.e., within a by-group. ?Is the following code a safe use of transformBy? Is there an alternative? First, does the initial "orderBy" statement guarantee that the Time order will be

Dear, I'm following the r tag on stackoverflow.com, and couldn't but notice there are quite some questions popping up that deal with scoping in relation to custom functions. I grinded my teeth on it already, and I have absolutely no clue what goes wrong. The general pattern is as follows : ff <- function(x){ y <- some_value some_function(y) } > ff(x) Error in eval(expr,

Dear R, I've got a data frame with children examined multiple times and at various ages. I'm trying to find the first age at which another variable (LDL-Cholesterol) is >= 130 mg/dL; for some children, this may never happen. I can do this with transformBy and ddply, but with 10,000 different children, these functions take some time on my PCs - is there a faster way to do this in R?

Dear list, I have a data.frame with x, y values and a 3-level factor "group", say. I want to create a new column in this data.frame with the values of y scaled to 1 by group. Perhaps the example below describes it best: > x <- seq(0, 10, len=100) > my.df <- data.frame(x = rep(x, 3), y=c(3*sin(x), 2*cos(x), > cos(2*x)), # note how the y values have a different

Hi, as an R-beginner, I have a recoding problem and hope you can help me: I am working on a SPSS dataset, which I loaded into R (load("C:/...) I have 2 existing Variables: "ID" and "X" , and one variable to be computed: meanX.dependID (=mean of X for all rows in which ID has the same value) ID = subject ID. Since it is a longitudinal dataset, there are repeated

Dear list, I have two things I am struggling... # First set.seed(123) myD <- data.frame( Light = sample(LETTERS[1:2], 10, replace=T), Feed = sample(letters[1:5], 20, replace=T), value=rnorm(20) ) # Mean for Light myD$meanLight <- unlist( lapply( myD$Light, function(x) mean( myD$value[myD$Light == x]) ) ) # Mean for Feed

Dear R users, I am encoutering the following problem: I have a dataset with a 'unique_id' and different 'visit_date' (formatted as.Date, "%d/%m/%Y") per unique_id. I would like to create a new variable with the most recent date of visit per unique_id as shown below. unique_id visit_date last_visit_date 1 01/06/2010 01/06/2011 1 01/01/2011 01/06/2011 1

dear R-team I need to find the min, max values for each patient from dataset and keep the output of it as a dataframe with the following columns - Patient nr - Region (remains same per patient) - Min score - Max score Patient Region Score Time 1 1 X 19 28 2 1 X 20 126 3 1 X 22 100 4 1 X 25 191 5 2 Y 12 1