CODE EXAMPLE FOR R

calculating RMSE, MAE, MSE, Rsquared manually in R

d = original-predicted
mse = mean((d)^2)
mae = mean(abs(d))
rmse = sqrt(mse)
R2 = 1-(sum((d)^2)/sum((original-mean(original))^2))

cat(" MAE:", mae, "
", "MSE:", mse, "
",