细分两个因素-“＆”对因素无意义

Question

I am trying to filter two variables in my data.frame by specified conditions.

I want to subset two variable factors: a) Ratings b) Location

I filtered the ratings variable in order to select those ratings which are relevant to me, ie, ratings == 0.

Now, I would now like select the 'Location' variable that only have a Ratings == 0, but am unable to do so. I know it is subsetting but cant get code right....But not filtering the ''location'' variable my location variable will number more than my Rating variable.

I tried the below code but I am getting an error:

Unrated_MraLevel1 <- xyz[(MRA == "0" & xyzLocation)]

error msg : In Ops.factor(MRA== "0", xyz$Location) : '&' not meaningful for factors

Answer 1

Based on your description this is what you want.

Example data:

dd <- data.frame(location=rep(letters[1:3],each=3),
                 MRA=c(rep(0,3),1:3,c(2,0,0)))

Aggregate data to find levels where all location values are equal to zero:

a <- aggregate(MRA~location,dd,FUN=function(x) all(x==0))

Extract the levels to keep:

keep.levels <- a$location[a$MRA]

Subset the data set:

dd[dd$location %in% keep.levels,]