请问xtivreg2命令第一阶段回归为什么不汇报R方?这是我的命令
xtivreg2 f.GW_excess (frequency=f.frequency frequency_pro) ///
size lev roa mb cf fa listage top1 dr ghold board pid big4 dual state m1-m11 n1-n19,first fe r
FIXED EFFECTS ESTIMATION
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Number of groups = 2328 Obs per group: min = 2
avg = 5.1
max = 9
Warning - collinearities detected
Vars dropped: _Iyear_2019 _Iyear_2020 _Iind1_11
First-stage regressions
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FIXED EFFECTS ESTIMATION
------------------------
Number of groups = 2328 Obs per group: min = 2
avg = 5.1
max = 9
First-stage regression of frequency:
Statistics consistent for homoskedasticity only
Number of obs = 11864