[R-meta] Observed effect size using escalc

[Myers, Brett]

Hello,

I am new to the metafor package and I am trying to decipher someone else's code. I'm specifically curious about the "yi" variable associated with the escalc() function. It appears that the yi vector is an output variable that escalc() appends to the dataset. The metafor documentation says that yi is the observed effect size, and we didn't enter this as an input variable, so I'm wondering what formula escalc() uses to determine yi. Would anyone here have some insight on how yi is calculated?

Thanks,
Brett Myers