I'm using the leaps package in R to run regsubsets:
a <- regsubsets(in_var~paste(predictors,collapse="+"),data=x,nbest=10,matrix=T)
And get an error message:
Error in model.frame.default(data = x, matrix = T, formula = rating ~  : variable lengths differ (found for '(matrix)')
(Note, it makes no difference if I copy out the predictors list manually or not).
I've just tried with the attitude dataset, e.g.:
data(attitude)
attitude <- na.omit(attitude)
regsubsets(rating~.,data=attitude,nbest=10,matrix=T)
And get the same error.  My dataset is similar, but has more variables and the in_var is a 1-3 score (elsewhere I collapse it to a binary, for which I could later run a logistic).  Not sure if I'm asking a statistics question or an R question here...
A few questions (e.g. Error in model.frame.default ...... variable lengths differ ; variable lengths differ in R ... ) deal with this, but I've already done na.omit on the dataframe, so I shouldn't have any missing values resulting in uneven vectors.
 
    