Folded Normal Distribution

If $Z$ is Normal with mean $L$ and $\sigma =S$ , then $\left|Z\right|$ is a folded normal with shape parameter $c=\left|L\right|/S$ , location parameter $0$ and scale parameter $S$ . This is a special case of the non-central chi distribution with one- degree of freedom and non-centrality parameter $c^2.$ Note that $c\ge 0$ . The standard form of the folded normal is

Implementation: scipy.stats.foldnorm