Absolute value or minus sign missing in docstrings for head and tail

[olbermann]

In the docstrings for the head and tail functions (in pandas/core/generic.py) there is an absolute value or minus sign missing:
e.g. in tail docstring

For negative values of `n`, this function returns all rows except
        the first `n` rows, equivalent to ``df[n:]``.

should read something like

For negative values of `n`, this function returns all rows except
        the first `np.abs(n)` rows, equivalent to ``df[np.abs(n):]``.

or

For negative values of `n`, this function returns all rows except
        the first `-n` rows, equivalent to ``df[-n:]``.

Similarly for head.

[parkdj1]

I think the original should be correct since it says 'for negative values of' n, implying we are thinking of n as some positive integer and considering the cases in which the input is the negative value of such n

[olbermann]

No, the original is wrong. It says 'for negative values of n', this means the same as 'in the case that n is negative'.

You are right that it would be easier to think of variables with positive values: Maybe one should say
For a positive integer `k`, the function `df.tail(-k)` returns all rows except the first `k` rows, equivalent to `df[k:]`.

[mzeitlin11]

+1 on that being clearer wording. Would you be interested in making a pr?

[parkdj1]

Agreed it never hurts to make documentation clearer. I can take if @olbermann doesn’t want to

[jackgoldsmith4]

take

[jackgoldsmith4]

I am going to make changes to the docstrings based on the feedback on #42216