Error: Invalid number of ‘breaks’ in R

You have some problems in your syntax.

Note that you have converted gender to a factor variable with values of “1” and “2” instead of “M” and “F”. If you run your code line-by-line, I’ll guess that it should work up to your last set of histograms.

Change those lines to:

hist(d$received[d$negotiated == TRUE & d$gender == 2], 
     main = 'Male Employees Who Negotiated Raises' )

hist(d$received[d$negotiated == TRUE & d$gender == 1], 
     main = 'Female Employees Who Negotiated Raises' )

Also, notice that I changed && to &. Run d$negotiated == TRUE & d$gender == 2 and d$negotiated == TRUE && d$gender == 2 to see how they are different from each other.