In R, how to add the fitted value column to the original dataframe?

Question

I have a multiple regression model. I want to add the fitted values and residuals to the original data.frame as two new columns. How can I achieve that? My model in R is like this:

BD_lm <- lm(y ~ x1+x2+x3+x4+x5+x6, data=BD)
summary(BD)

I also got the fitted value

BD_fit<-fitted(BD_lm)

But I want to add this BD_fit values as a column to my original data BD. I don't know how. When I tried to call BD_fit, it just gave me a lot of numbers. I am running a large dataset, so it is hard to list all of them here.

Answer 1

Suppose:

fm <- lm(demand ~ Time, BOD)

Then try this:

cbind(BOD, resid = resid(fm), fitted = fitted(fm))

or this:

BOD$resid <- resid(fm)
BOD$fitted <- fitted(fm)

ADDED:

If you have NA values in demand then your fitted values and residuals will be of a different length than the number of rows of your data, meaning the above will not work. In such a case use: na.exclude like this:

BOD$demand[3] <- NA # set up test data
fm <- lm(demand ~ Time, BOD, na.action = na.exclude)

na.exclude will automatically pad the predictions and residuals with NA values so that they are of the same length as the original data. Now the previous lines should work.