Hi! Im currently experiencing issues with a regression in R studio, where the regression results are not shown as expected. The following is the regression model:

lm(formula = bid_ask_spread ~ time + after + after:time + as.factor(firm_no) + as.factor(country_no), data = df_complete)

The following are the first few lines of the results (there are many more fixed effects):

Residuals:

Min 1Q Median 3Q Max

-6420.0 -102.0 -8.3 72.0 19165.4

Coefficients: (11 not defined because of singularities)

Estimate Std. Error t value Pr(>|t|)

(Intercept) -1.396e+04 6.514e+02 -21.434 < 2e-16 ***

time 1.163e-05 5.428e-07 21.435 < 2e-16 ***

after 4.680e+02 1.227e+01 38.141 < 2e-16 ***

as.factor(firm_no)2 1.453e+00 6.920e+01 0.021 0.983243

as.factor(firm_no)3 3.280e-01 6.920e+01 0.005 0.996218

These results are unexpected in two ways. (1) the estimate for the interaction term is missing and (2) R does not show the fixed effects for firm_no 1.

Could you help me find the reason for this? i'd appreciate massively.

Thanks and have a good day,

Ben