I am analysing a data of number of aphids with variation over time (32 avaliations performed every week), area (two areas), and plant position (fixed factor), with 3 replications. Because of that, I am running both GEE and GLMM (to compare the results). The problem is that for each time in each area I have the data on precipitation and temperature. And these data are important because the aphid population is highly affected by these ambient conditions. I really want to study the effect of temperature and precipitation, and I am thinking of using them as fixed factors, but it does not sound correct because they are a range of values. I have thought about using the values as an offset in the model, but I don't know if it is right and probably I will not be able to make any conclusions on how the temperature and precipitation affected the data.
Here is a small example of the data set:
- REP- repetition
- posi - plant position
- prec - precipitation
- medt maxt mint - temperature information
- area- area
- cont- number of aphids
- time- week of the count
rep posi prec medt maxt mint area cont time 1 s 11.03 21.60 28.20 15.10 1 22 1 1 m 11.03 21.60 28.20 15.10 1 0 1 1 i 11.03 21.60 28.20 15.10 1 0 1 2 s 11.03 21.60 28.20 15.10 1 2 1 2 m 11.03 21.60 28.20 15.10 1 0 1 2 i 11.03 21.60 28.20 15.10 1 0 1 3 s 11.03 21.60 28.20 15.10 1 1 1 . . . . . . . . . . . . . . . . 1 s 143.70 22.66 26.24 19.09 2 0 32 1 m 143.70 22.66 26.24 19.09 2 23 32 1 i 143.70 22.66 26.24 19.09 2 18 32 2 s 143.70 22.66 26.24 19.09 2 0 32 2 m 143.70 22.66 26.24 19.09 2 0 32 2 i 143.70 22.66 26.24 19.09 2 0 32 3 s 143.70 22.66 26.24 19.09 2 3 32 3 m 143.70 22.66 26.24 19.09 2 0 32 3 i 143.70 22.66 26.24 19.09 2 3 32
