Does this probability distribution function pdf have a name? It looks like it could be quite useful. I was looking for a pdf to describe the variation of numbers of shark species (of different types) with depth, and neither truncated normal, gumbel, or weibull was a fit. A similar pdf could be used to describe perhaps wind speed for example.

a e ^-x +(1-a) x e ^-x
where 0 ≤ a ≤ 1.

mollwollfumble said:

Does this probability distribution function pdf have a name? It looks like it could be quite useful. I was looking for a pdf to describe the variation of numbers of shark species (of different types) with depth, and neither truncated normal, gumbel, or weibull was a fit. A similar pdf could be used to describe perhaps wind speed for example.

a e ^-x +(1-a) x e ^-x
where 0 ≤ a ≤ 1.

Looks like a rainbow carrot from Vega Centauri.

Bubblecar said:

mollwollfumble said:

Does this probability distribution function pdf have a name? It looks like it could be quite useful. I was looking for a pdf to describe the variation of numbers of shark species (of different types) with depth, and neither truncated normal, gumbel, or weibull was a fit. A similar pdf could be used to describe perhaps wind speed for example.

a e ^-x +(1-a) x e ^-x
where 0 ≤ a ≤ 1.

Looks like a rainbow carrot from Vega Centauri.

This is how it fits number of shark species as a function of depth, a = 0.5.
As good a fit as erfc(x), if not better. erfc has the disadvantage of having no free parameter, so can’t match number of dogfish species as a function of depth, for example.