问题
When I run a quantile regression in R, using the quantreg package, and then I run summary(quantregObject), I get this error message:
Error in base::backsolve(r, x, k = k, upper.tri = upper.tri, transpose = transpose, : singular matrix in 'backsolve'. First zero in diagonal [1]
Any suggestion how could I fix this problem?
回答1:
In short, try:
summary(quantregObject, se = "iid")
which puts a strong assumption on your residuals. Or if you need accuracy use a boot strap to get the standard errors:
summary(quantregObject, se = "boot")
If you call summary on a an object returned by quantreg:rq
summary(quantregObject)
This will call summary.rq.
From ?summary.rq.
You can see that there are 4 options to compute the standard errors (se).
Depending on the sample size (N < 1000) the default is se = "rank" or se = "nid".
"nid" does something which sounds complicated and may then yield a diagonal matrix which backsolve cannot handle.
来源：https://stackoverflow.com/questions/28393176/error-in-summary-quantreg-backsolve