I want to draw a boxplot with whiskers where a lower bound is equal to $Q1 - 1.5 IQR$ and an upper bound is equal to $Q3 + 1.5 IQR$, where $Q1$ is a lower quantile, $Q3$ is an upper quantile and $IQR$ ia an interquantile range.
My observations are positive, but the value $Q1 - 1.5 IQR$ is below $0$. My question is:
Where should I put a lower bound of whiskers on a boxplot: in the point $Q1 - 1.5 IQR$ (which is negative) or in the point equal to $0$, because all my observations are positive?
The whiskers should extend to the most extreme data points satisfying the criterion that they lie within $Q1-1.5IQR$ and $Q3+1.5IQR$ from the respective box edges.
e.g. see here and read about 'range'