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I am trying to perform universal kriging in R using the gstat package and running into the following error:

krige(formula = CDD_LT_stC ~ Imperv1km + Elev_new, locations = sp.cal_data, newdata = sp.studygrid, model = modelfit, nmax = 200)

Error in eval(predvars, data, env) : object 'Imperv1km' not found

Any ideas why is this happening and how to fix this?

However, I was able to perform ordinary kriging with:

krige(formula = CDD_LT_stC ~ 1, locations = sp.cal_data, newdata = sp.studygrid, model = modelfit, nmax = 200)
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    What is in your sp.cal_data data frame? It is saying there is no column called Imperv1km. Hard for us to answer without more details or a copy of your data. – Spacedman Nov 12 '18 at 7:06
  • @Spacedman It's a "SptatialPointsDataFrame" and does include the column Imperv1km as well as the Elev_new. As I mentioned, the code worked if I use the ordinary kriging (i.e., formula = CDD_LT_stC ~ 1) but isn't working when I am using universal kriging (i.e., formula = CDD_LT_stC ~ Imperv1km + Elev_new). In both cases, the dataset are the same. – Saad Nov 12 '18 at 15:37
  • Edit your post to show some information about sp.cal_data - at a very minimum the output of summary on it. – Spacedman Nov 12 '18 at 17:32
  • And are you using the same modelfit object? – Spacedman Nov 12 '18 at 17:34
  • And do those columns exist in your newdata? – Spacedman Nov 12 '18 at 17:36