Here's my example. Given a regression model and a variable, I want to use unstack() on the vector of residuals and make some magic with the result. But unstack hates me.
PCSE <- function (tmodel,groupVar) { myres1 <- resid(tmodel) resUnstacked <- unstack(myres1, form = myres1 ~ groupVar)); E <- as.matrix(resUnstacked) SIGMA <- (1/nrow(E))*(t(E) %*% E) OMEGA <- diag(x=1, nrow=nrow(E), ncol=nrow(E)) %x% SIGMA
X <- model.matrix(tmodel) XPRIMEXINV <- solve(t(X) %*% X) PCSECOVB <- XPRIMEXINV %*% (t(X) %*% OMEGA %*% X ) %*% XPRIMEXINV }
The error is: PCSE(eld.ols1,dat2$STATEID) Error in eval(expr, envir, enclos) : Object "groupVar" not found
Here's what I don't understand the most.
If I hack this so that the "resUnstacked" is created by a "matrix" command, then the function works. Why would matrix() work when unstack does not. And why does model.matrix() work if unstack does not.
Thanks in advance, as usual.
--
Paul E. Johnson email: [EMAIL PROTECTED]
Dept. of Political Science http://lark.cc.ku.edu/~pauljohn
1541 Lilac Lane, Rm 504 University of Kansas Office: (785) 864-9086
Lawrence, Kansas 66044-3177 FAX: (785) 864-5700
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