[R] NA when trying to calculate AIC value for DLNM

[Malgosia Lubczynska]

Dear all,
 
I am trying to run a sensitivity analysis for a DLNM combined with a case crossover design and select the best parameters based on AIC values for different model set-ups.
 
model <- glm(mortality ~ cb.temp + ns(soo, 7*7) + dow, family=quasipoisson(), my.data)
 
where cb.temp is the crossbasis matrix for the exposure (temperature)
 
However, the output for the AIC calculations equals NA.
Does anyone know how to obtain a correct AIC for a DLNM model?
 
Thank you,
Gosia
 
 
 		 	   		  
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