I’m trying to plot the original date with the predictions of the best models using curve() because I’m working with polynomial models, but I keep getting this error:

Error in curve(predict(best_models[[i]]$best_model, newdata = data.frame(get(normalized_columns[i]))), :
‘expr’ must be a function, or a call or an expression containing ‘x

This is the part of the code that it is generating the error:

par(mfrow = c(2, 3))   for (i in 1:6) {   curve(predict(best_models[[i]]$best_model, newdata = data.frame(get(normalized_columns[i]))),          from = min(filtered_resp_data[[normalized_columns[i]]]),          to = max(filtered_resp_data[[normalized_columns[i]]]),          col = "blue", lwd = 2,         xlab = normalized_columns[i], ylab = "xxx",         main = paste("Real Data vs. Best Model (Degree", best_models[[i]]$best_degree, ")"))