I am using the twang package to create propensity scores, which are used as weigtings in a binomial glm using survey::svyglm. The code looks something like this: pscore <- ps(ppci ~ var1+var2+.........., data=dt....) dt$w <- get.weights(pscore, stop.method="es.mean") design.ps <- svydesign(ids=~1, weights=~w, data=dt,) glm1 <- svyglm(m30 ~ ppci, design=design.ps,family=binomial) This produces the following warning: Warning message: In eval(expr, envir, enclos) : non-integer #successes in a binomial glm! Does anyone know what I could be doing wrong ? I wasn't sure if this message would be better on stats.SE, but on balance I thought I would try here first.