Error message when using "car" package

I keep getting error messages whenever I download "car" package to perform a levene test
#Open data file

#Check for equal variances
Error in model.frame.default(form) :
invalid type (NULL) for variable 'mtcars$qsec_before'

The mtcars data set doesn't contain a variable called qsec_before and you are not defining it anywhere in your code, that is why you get the NULL error, you should check on that.

 [1] "mpg"  "cyl"  "disp" "hp"   "drat" "wt"   "qsec" "vs"   "am"   "gear" "carb"

Thanks for your quick reply. I am a newbie at this, I am trying to test the distribution of automatic and manual transmission. qsec represents the quater mile time of various cars

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