Hi, dat <- read.table(text="A???? B????????????? ?1???? 0 ?2???? 2 ?3???? 1 ?4???? NA",sep="",header=TRUE) ? within(dat,{C<-A/B;C[!is.finite(C)]<-0}) # ?within(dat,{C<-A/B;C[!is.finite(C)]<-NA}) A.K. Hi R users, Just wondering is it possible to divide two columns with some NA or Zero values? ?E.g.: A ? ? B ? ? ? ? ? ? ? 1 ? ? 0 2 ? ? 2 3 ? ? 1 4 ? ? 0 I want something like this: A ? ?B ? ?C 1 ? ?0 ? ?0 (or NA) 2 ? ?2 ? ?1 3 ? ?1 ? ?3 4 ? ?0 ? ?0 (or NA) Even though it is not meaningful to divide zero but the data I got have these missing values in a time series... Ignoring them will not have a material effect on my analysis. Thanks!