I am using the Rdrobust package to estimate the effect of a national policy on county level outcomes. In my covariates I have included dummies indicating states to control for state level fixed effect. However, when we run the code, I get following error message:
Error in chol.default(ZWZ) :
the leading minor of order 33 is not positive definite.
Where Z is the matrix containing my covaraites and the 33-th variable is the dummy for state 1.
my code is:
out = rdrobust(y, x, covs=z, kernel = "triangular", p=2, bwselect="mserd",
cluster= cluster)
I am not sure how to get rid of this error message. More importantly, I am wondering if there is any other way to control for fixed effects (e.g. state-level) in Rdrobust package.
Thanks in advance for your help
The recent rdrobust version 1.0.1 should take care of this error. To generate fixed effects from a categorical variable "state" you can do something like:
state.f = factor(state)
state.d = model.matrix(~state.f+0)
out = rdrobust(y, x, covs = state.d)