st: xi function dummies being dropped due to collinearity

[Lisa Marie Yarnell <lisa.yarnell@utexas.edu>]

Hello Statalisters:  I'm using the xi function to create school
dummies to control for school effects in a quantile regression model,
using the code below.  However, the dummies are all being dropped
because of collinearity.  Why would this happen, and how can I
alleviate this?  Thank you, Lisa

. xi: sqreg bmiscore ecopct aa hispanic spanish otherl boy bmi_p20
bmi_p50 bmi_p80 i.schoolid if grade == 4, quantile (.5 .6 .7 .8 .9)
reps(50)
i.schoolid        _Ischoolid_1-280    (_Ischoolid_1 for
sch~d==003905001 omitted)
note: _Ischoolid_2 dropped because of collinearity
note: _Ischoolid_4 dropped because of collinearity
note: _Ischoolid_5 dropped because of collinearity
note: _Ischoolid_8 dropped because of collinearity
note: _Ischoolid_10 dropped because of collinearity
note: _Ischoolid_11 dropped because of collinearity
note: _Ischoolid_13 dropped because of collinearity
note: _Ischoolid_14 dropped because of collinearity
note: _Ischoolid_17 dropped because of collinearity
note: _Ischoolid_20 dropped because of collinearity
note: _Ischoolid_21 dropped because of collinearity
note: _Ischoolid_22 dropped because of collinearity
note: _Ischoolid_23 dropped because of collinearity
note: _Ischoolid_24 dropped because of collinearity
note: _Ischoolid_25 dropped because of collinearity
note: _Ischoolid_26 dropped because of collinearity
note: _Ischoolid_27 dropped because of collinearity
note: _Ischoolid_29 dropped because of collinearity
note: _Ischoolid_32 dropped because of collinearity
note: _Ischoolid_33 dropped because of collinearity
note: _Ischoolid_37 dropped because of collinearity
note: _Ischoolid_38 dropped because of collinearity
note: _Ischoolid_39 dropped because of collinearity
note: _Ischoolid_40 dropped because of collinearity
note: _Ischoolid_41 dropped because of collinearity
note: _Ischoolid_43 dropped because of collinearity
note: _Ischoolid_44 dropped because of collinearity
note: _Ischoolid_45 dropped because of collinearity
note: _Ischoolid_46 dropped because of collinearity
note: _Ischoolid_47 dropped because of collinearity
note: _Ischoolid_48 dropped because of collinearity
note: _Ischoolid_49 dropped because of collinearity
note: _Ischoolid_50 dropped because of collinearity
note: _Ischoolid_56 dropped because of collinearity
note: _Ischoolid_58 dropped because of collinearity
note: _Ischoolid_59 dropped because of collinearity
note: _Ischoolid_60 dropped because of collinearity
note: _Ischoolid_62 dropped because of collinearity
note: _Ischoolid_64 dropped because of collinearity
note: _Ischoolid_65 dropped because of collinearity
note: _Ischoolid_66 dropped because of collinearity
note: _Ischoolid_67 dropped because of collinearity
note: _Ischoolid_68 dropped because of collinearity
note: _Ischoolid_69 dropped because of collinearity
note: _Ischoolid_70 dropped because of collinearity
note: _Ischoolid_73 dropped because of collinearity
note: _Ischoolid_74 dropped because of collinearity
note: _Ischoolid_79 dropped because of collinearity
note: _Ischoolid_80 dropped because of collinearity
note: _Ischoolid_82 dropped because of collinearity
note: _Ischoolid_84 dropped because of collinearity
note: _Ischoolid_85 dropped because of collinearity
note: _Ischoolid_88 dropped because of collinearity
note: _Ischoolid_89 dropped because of collinearity
note: _Ischoolid_90 dropped because of collinearity
note: _Ischoolid_95 dropped because of collinearity
note: _Ischoolid_96 dropped because of collinearity
note: _Ischoolid_97 dropped because of collinearity
note: _Ischoolid_98 dropped because of collinearity
note: _Ischoolid_99 dropped because of collinearity
note: _Ischoolid_100 dropped because of collinearity
note: _Ischoolid_101 dropped because of collinearity
note: _Ischoolid_102 dropped because of collinearity
note: _Ischoolid_107 dropped because of collinearity
note: _Ischoolid_108 dropped because of collinearity
note: _Ischoolid_109 dropped because of collinearity
note: _Ischoolid_110 dropped because of collinearity
note: _Ischoolid_111 dropped because of collinearity
note: _Ischoolid_112 dropped because of collinearity
note: _Ischoolid_114 dropped because of collinearity
note: _Ischoolid_119 dropped because of collinearity
note: _Ischoolid_121 dropped because of collinearity
note: _Ischoolid_122 dropped because of collinearity
note: _Ischoolid_123 dropped because of collinearity
note: _Ischoolid_125 dropped because of collinearity
note: _Ischoolid_126 dropped because of collinearity
note: _Ischoolid_129 dropped because of collinearity
note: _Ischoolid_130 dropped because of collinearity
note: _Ischoolid_132 dropped because of collinearity
note: _Ischoolid_133 dropped because of collinearity
note: _Ischoolid_134 dropped because of collinearity
note: _Ischoolid_135 dropped because of collinearity
note: _Ischoolid_136 dropped because of collinearity
note: _Ischoolid_137 dropped because of collinearity
note: _Ischoolid_139 dropped because of collinearity
note: _Ischoolid_140 dropped because of collinearity
note: _Ischoolid_141 dropped because of collinearity
note: _Ischoolid_142 dropped because of collinearity
note: _Ischoolid_144 dropped because of collinearity
note: _Ischoolid_145 dropped because of collinearity
note: _Ischoolid_146 dropped because of collinearity
note: _Ischoolid_147 dropped because of collinearity
note: _Ischoolid_148 dropped because of collinearity
note: _Ischoolid_149 dropped because of collinearity
note: _Ischoolid_150 dropped because of collinearity
note: _Ischoolid_151 dropped because of collinearity
note: _Ischoolid_152 dropped because of collinearity
note: _Ischoolid_157 dropped because of collinearity
note: _Ischoolid_163 dropped because of collinearity
note: _Ischoolid_165 dropped because of collinearity
note: _Ischoolid_166 dropped because of collinearity
note: _Ischoolid_167 dropped because of collinearity
note: _Ischoolid_168 dropped because of collinearity
note: _Ischoolid_169 dropped because of collinearity
note: _Ischoolid_174 dropped because of collinearity
note: _Ischoolid_178 dropped because of collinearity
note: _Ischoolid_181 dropped because of collinearity
note: _Ischoolid_182 dropped because of collinearity
note: _Ischoolid_183 dropped because of collinearity
note: _Ischoolid_187 dropped because of collinearity
note: _Ischoolid_188 dropped because of collinearity
note: _Ischoolid_190 dropped because of collinearity
note: _Ischoolid_191 dropped because of collinearity
note: _Ischoolid_194 dropped because of collinearity
note: _Ischoolid_195 dropped because of collinearity
note: _Ischoolid_196 dropped because of collinearity
note: _Ischoolid_197 dropped because of collinearity
note: _Ischoolid_198 dropped because of collinearity
note: _Ischoolid_199 dropped because of collinearity
note: _Ischoolid_200 dropped because of collinearity
note: _Ischoolid_201 dropped because of collinearity
note: _Ischoolid_205 dropped because of collinearity
note: _Ischoolid_207 dropped because of collinearity
note: _Ischoolid_208 dropped because of collinearity
note: _Ischoolid_211 dropped because of collinearity
note: _Ischoolid_212 dropped because of collinearity
note: _Ischoolid_213 dropped because of collinearity
note: _Ischoolid_214 dropped because of collinearity
note: _Ischoolid_217 dropped because of collinearity
note: _Ischoolid_218 dropped because of collinearity
note: _Ischoolid_220 dropped because of collinearity
note: _Ischoolid_221 dropped because of collinearity
note: _Ischoolid_222 dropped because of collinearity
note: _Ischoolid_223 dropped because of collinearity
note: _Ischoolid_224 dropped because of collinearity
note: _Ischoolid_225 dropped because of collinearity
note: _Ischoolid_226 dropped because of collinearity
note: _Ischoolid_231 dropped because of collinearity
note: _Ischoolid_234 dropped because of collinearity
note: _Ischoolid_235 dropped because of collinearity
note: _Ischoolid_240 dropped because of collinearity
note: _Ischoolid_242 dropped because of collinearity
note: _Ischoolid_244 dropped because of collinearity
note: _Ischoolid_245 dropped because of collinearity
note: _Ischoolid_246 dropped because of collinearity
note: _Ischoolid_247 dropped because of collinearity
note: _Ischoolid_248 dropped because of collinearity
note: _Ischoolid_249 dropped because of collinearity
note: _Ischoolid_255 dropped because of collinearity
note: _Ischoolid_259 dropped because of collinearity
note: _Ischoolid_260 dropped because of collinearity
note: _Ischoolid_261 dropped because of collinearity
note: _Ischoolid_262 dropped because of collinearity
note: _Ischoolid_263 dropped because of collinearity
note: _Ischoolid_269 dropped because of collinearity
note: _Ischoolid_270 dropped because of collinearity
note: _Ischoolid_272 dropped because of collinearity
note: _Ischoolid_273 dropped because of collinearity
note: _Ischoolid_275 dropped because of collinearity
note: _Ischoolid_276 dropped because of collinearity
note: _Ischoolid_278 dropped because of collinearity
note: _Ischoolid_279 dropped because of collinearity
(fitting base model)


-- 
Lisa M. Yarnell
Department of Psychology
University of Southern California
3620 McClintock Ave.
Mailroom SGM 501, Office 826B
Los Angeles, CA 90089-1061
Mobile, preferred: (617) 548-2893
Office: x0-0850 or (213) 740-0850
Fax: (213) 746-9082
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