[arellano] Simplify probability computations

[TaichiSakaguchi]

Simplify probability computations.

[jstac]

Thanks @TaichiSakaguchi . I'll run the workflow and we'll get back to you.

[mmcky]

@jstac a preview build is available here

https://657a595a6af2be36a2b7a463--wonderful-lalande-528d1c.netlify.app/arellano.html

in #153

[mmcky]

thanks @TaichiSakaguchi this looks more concise.

@jstac the plots look the same between the current live site and the preview build.

From my perspective I am not sure if this improves the readability of the code as it is combining two operations into a single line. I am usually in favour of more lines as I find it typically a bit "easier" to understand (as a reader).

[oyamad]

If one wants to write it with two lines:

default_states = v_c[B_idx, :] < v_d
delta = P[y_idx, default_states].sum()

But this looks redundant to me...

[jstac]

Thanks @TaichiSakaguchi