mix.R

        }
    }

    ## Missing mz?
    if (checkMz) {
        ind<-which(is.na(df$mz))
        if (length(ind)>0) {
            for (i in ind) {
                warning("mz missing at row: ",i, "; ID: ",df$ID[[i]]," .")
            }
            stop("Missing mz-s found.")
        }
    }

    df
}