search for: es_time

Hi I'm trying to extract complete rows from a dataframe by group based on the maximum in a column within that group. Thus I have a dataframe: cvd_basestudy ... es_time ... _____________ study1 ... 0.3091667 study2 ... 0.3091667 study2 ... 0.2625000 study3 ... 0.3033333 study3 ... 0.2625000 __________ etc I can extract the basestudy and the max(es_time) using ddply ddply(datares_sinus_variable, .(cvd_basestudy), function(x){max(...

...er of ways in R to do this and can't find a good solution. (I could do it out of R in perl or awk but would like to know how to do this in R). I have a large data frame 49 variables and 7000 observations however for simplicity I can express it in the following data frame Base, Image, LVEF, ES_Time A, 1, 4.32, 0.89 A, 2, 4.98, 0.67 A, 3, 3.7, 0.5 A, 3. 4.1, 0.8 B, 1, 7.4, 0.7 B, 3, 7.2, 0.8 B, 4, 7.8, 0.6 C, 1, 5.6, 1.1 C, 4, 5.2, 1.3 C, 5, 5.9, 1.2 C, 6, 6.1, 1.2 C, 7. 3.2, 1.1 For each value of LVEF and ES_Time I would like to normalise the value to the maximum for that factor grouped by...