Error: please supply starting values

Question

I am conducting a log binomial regression in R. I want to control for covariates in the model (age and BMI- both continuous variables) whereas the dependent variable is Outc

Answer 1

After some trial and error, using set.seed(123):

coefini=coef(glm(Outcome~Group+Age, data=data.1,family =binomial(link = "log") ))
fit2<-glm(Outcome~Group+Age+BMI, data=data.1, family=binomial(link="log"),start=c(coefini,0))

summary(fit2)

Call:
glm(formula = Outcome ~ Group + Age + BMI, family = binomial(link = "log"), 
    data = data.1, start = c(coefini, 0))

Deviance Residuals: 
    Min       1Q   Median       3Q      Max  
-1.2457  -0.9699  -0.7725   1.2737   1.6799  

Coefficients:
              Estimate Std. Error z value Pr(>|z|)
(Intercept) -1.5816964  1.0616813  -1.490    0.136
Group1       0.4987848  0.3958399   1.260    0.208
Age          0.0091428  0.0138985   0.658    0.511
BMI         -0.0005498  0.0331120  -0.017    0.987

(Dispersion parameter for binomial family taken to be 1)

    Null deviance: 65.342  on 49  degrees of freedom
Residual deviance: 63.456  on 46  degrees of freedom
AIC: 71.456

Number of Fisher Scoring iterations: 3