search for: combinevar

...f SDs, I have no idea how to do it. I've found functions such as wtd.var() from the package Hmisc for calculating variances from values with different weights, but it does not sum variances, it just calculates the overall variance of a set of measurements with different weights. I also found combinevar() from the package fishmethods that can be used to add variances, but this one does not allow to associate a weight to those variances. So, I do not know how to do both things at the same time. Any idea? Any package? Or any suggestion so I can make my own function? Thank you very much Fernando...