I have data frame looking like this
V1 V2
.. 1
.. 2
.. 1
.. 3
etc.
For each distinct V2 value i would like to calculate variance of data in V1. I have just started my adventure with R, any hints how to do this? for my specific case i guess i can do manually something like
var1 = var(data[data$V2==1, "V1"])
var2 = ...
etc because I know all possible V2 values ( there are not many ), however I am curious what would be more generic solutions. Any ideas?
And the old standby, tapply
:
dat <- data.frame(x = runif(50), y = rep(letters[1:5],each = 10))
tapply(dat$x,dat$y,FUN = var)
a b c d e
0.03907351 0.10197081 0.08036828 0.03075195 0.08289562
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