Quantile regression errors and How to plot?

[rloved]

Hi all,

I'm running the quantile regression and trying to plot the coefficients and confidence intervals of four independent variables (yeaedu, sex, union, unimem).

The data a .dta file, but I used as_factor to convert data before running the regression.

My codes:

bri0 = read.dta("britearn.dta")
bri0.1 = as_factor(bri0,only_labelled = TRUE)

#quantile regression
model.bri.q = rq(lrehrwge ~ yeaedu + sex + union + unimem

• seniorit + yeactexp + race + mastat
• jbsect + region,
  data = bri0, tau = seq(0.1, 0.9, by=0.1),
  na.action = na.exclude)
  summary(model.bri.q)

My data file:

redirect.is

My errors are:
Warning messages:

.... Solution may be nonunique

1: In summary.rq(xi, U = U, ...) : 37 non-positive fis

2: In summary.rq(xi, U = U, ...) : 9 non-positive fis

3: In summary.rq(xi, U = U, ...) : 2 non-positive fis

4: In summary.rq(xi, U = U, ...) : 9 non-positive fis

5: In summary.rq(xi, U = U, ...) : 5 non-positive fis

6: In summary.rq(xi, U = U, ...) : 7 non-positive is

So, my questions are:

• How did I get these errors?
• How can I plot the effects of only four variables yeaedu + sex + union + unimem on the dependent variable (most of the rest are categorical variables, I don't want to plot them)?

I'm a beginner user of R, so I hope that you can help me to resolve my problem well.

Thank you so much!