Error in dataframe *tmp* replacement has x data has y

Question

I'm a beginner in R. Here is a very simple code where I'm trying to save the residual term:

# Create variables for child's EA:

dat$cldeacdi <- rowMeans(dat[,c('cdcresp', 'cdcinv')],na.rm=T)
dat$cldeacu <- rowMeans(dat[,c('cucresp', 'cucinv')],na.rm=T)

# Create a residual score for child EA:

dat$cldearesid <- resid(lm(cldeacu ~ cldeacdi, data = dat))

I'm getting the following message:

Error in `$<-.data.frame`(`*tmp*`, cldearesid, value = c(-0.18608488908881,  : 
  replacement has 366 rows, data has 367

I searched for this error but couldn't find anything that could resolve this. Additionally, I've created the exact same code for mom's EA, and it saved the residual just fine, with no errors. I'd be grateful if someone could help me resolve this.

Answer 1

I have a feeling you have NAs in your data. Look at this example:

#mtcars data set
test <- mtcars
#adding just one NA in the cyl column
test[2, 2] <- NA

#running linear model and adding the residuals to the data.frame
test$residuals <- resid(lm(mpg ~ cyl, test))
Error in `$<-.data.frame`(`*tmp*`, "residuals", value = c(0.382245430809409,  : 
  replacement has 31 rows, data has 32

As you can see this results in a similar error to yours.

As a validation:

length(resid(lm(mpg ~ cyl, test)))
#31
nrow(test)
#32

This happens because lm will run na.omit on the data set prior to running the regression, so if you have any rows with NA these will get eliminated resulting in fewer results.

If you run na.omit on your dat data set (i.e. dat <- na.omit(dat) at the very beginning of your code then your code should work.