dat$mean_diff <- dat$m2 - dat$m1
dat$sd_pooled <- sqrt(((dat$n1 - 1) * dat$s1^2 + (dat$n2 - 1) * dat$s2^2)/(dat$n1 + dat$n2 - 2))
dat$smd <- dat$mean_diff / dat$sd_pooled
dat$se <- sqrt((1/dat$n1 + 1/dat$n2) * (1 + dat$sd_pooled^2/(2*dat$n1) + dat$sd_pooled^2/(2*dat$n2)))
library(meta)
meta_obj <- metagen(TE= dat$smd, seTE = dat$se,
studlab = dat$Gait_speed, data = dat,
comb.random = TRUE, comb.fixed = FALSE,hakn = FALSE)forest(meta_obj,sortvar =TE, comb.fixed = FALSE,print.tau2 = TRUE,leftlabs = c("Author", "TE", "seTE"),rightlabs=c("SMD","95%-CI","Weight"),xlab = "decrease increase",ylab="Standardized mean difference")