search for: manuelperera

Dear R users, I have a dataframe with one character field, and I would like to create two new fields (columns) in my dataset, by spliting the existing character field into two using an existing substring. ... something that in SAS I could solve e.g. combining substr(which I am aware exist in R) and "index" for determining the position of the pattern within the string. e.g. if my

Hi enthusiasts, Trying to create a single chart in lattice with different plotting definitions for the different series (two series should be drawn with lines and the other without them) I am using a dataset, which includes a grouping variable e.g. clinic with three levels, the variable "year" and a continous variable: "mct". In the graph the variable "year" is in

Dear all, I am doing something wrong. I am trying to apply a formula for sample size calculation as in the book "Design and Analysis of Clinical Trials", from Chow et all. There a suggested sample size strategy uses the formula 0.30/0.45=F(0.80,2n,2n)/F(0.025,2n,2n) which gives n=96, as in the book. (here F(alfa,k,n) is the upper (alfa)th quantile of an F distribution with k,n

Dear all, I am exporting to latex a dataframe via xtable(Sweave). My dataframe includes 4 rows and 4 columns. The first two rows containing real values(e.g. a laboratory parameter's mean value), and the two rows at the bottom containing only integers (number of cases). using display=c('fg','fg','fg','fg') as an argument to xtable I tried to reach my goal, of

Dear all, I am exporting to latex a matrix via xtable. My matrix includes e.g. 4 rows and 4 columns. The first two rows containing real values(e.g. a laboratory parameter's mean value), and the two rows at the bottom containing only integers (number of cases). > mymat<-matrix(c(c(10.52,2.52,12.35,3.63),c(3.52,16.25,13.62,6.36),c(11,12,15,16),c(14,15,16,18)),4,4,byrow=TRUE) > mymat