Mean and standard deviation of triplicated vector data

Question

I have an experiment where I measured a bit less than 200 variables in triplicate. In other words, I have three vectors of ~ 200 values.

I want a quick way to determine if I should use mean or median for my calculations. I can do the mean easily ((v1 + v2 + v3) / 3), but how do I calculate the SD to have it in a vector of ~ 200 SDs? And what about the median? After having these values, I need to do growth curves (measurements were taken over certain period of time).

Answer 1

Here is a dplyr solution:

require(dplyr)

d <- data.frame(
  x1 = rnorm(10),
  x2 = rnorm(10),
  x3 = rnorm(10)
  )

d %>%
  rowwise() %>%
  mutate(
    mean = mean(c(x1, x2, x3)),
    median = median(c(x1, x2, x3)),
    sd = sd(c(x1, x2, x3))
    )

It sounds like you also have a substantive question about longitudinal data. If so, crossvalidated would be a good platform for this question.