I am trying to run a meta-regression using metafor with the following code:
rma(lnrr, v, mods = ~ duration_exp + feedstock_rename 
+                       + application_rate + soil_texture + soil_sample_depth_min
+                       + soil_sample_depth_max + average_precipitation, method = "REML", data=.)
But the code is returning the following error:
Error during wrapup: Processing terminated since k = 0.
When I remove the variable average_precipitation from the model which is a continuous variable, the model runs. Then I tried this variable in a separate model but it still gives the same error. I am a bit struggling to figure it out. Could anyone help with this?
 
    