Exercises

Let's return to the num.distinct function we created earlier. The comment inside the function indicated that we should be careful about using it with a non-integer numeric input (a float). The problem lies with how unique handles such inputs. Here's an example:

unique(c(.3, .4 - .1, .5 - .2, .6 - .3, .7 - .4)) # what happened?

Generally, to check for equality between two numeric value (or two numeric columns), we need to be more careful.

.3 == .4 - .1 # returns unexpected result

The right way to check if two real numbers are equal is to see if their difference is below a certain threshold.

abs(.3 - (.4 - .1)) < .0000001 # the right way of doing it

Another more convenient way to check equality between two real numbers is by using the all.equal function.

all.equal(.3, .4 - .1) # another way of doing it

(1) Use all.equal to determine if total_amount is equal to the sum of fare_amount, extra, mta_tax, tip_amount, tolls_amount, and improvement_surcharge.

(2) What are some other ways we could check (not necessarily exact) equality between two numeric variables?