[R] Picking a subset of explanatory variables corresponding to a subset or a transformed subsert of the response

[Luwis Tapiwa Diya]

I have a dataframe in which I have used a cerain procedure to select
the response a subset of the response and obtained a vector y.Now I
need to fit a glm of the response y given x(the covariates) but now I
get an error that the variables are not of equal length.How can I come
up with a way to pick the x values corresponding to only the subset of
the response I am interested in.

Regards,

Luwis