impute missing column values with mean of subset of values

[apintabir]

Hi, I recently started using arquero and I've mostly been able to get up to speed with the (very helpful) documentation. However, I can't wrap my head around how to do the following:

I have a table with a column that has a bunch of missing values, e.g.:
{ b: [11.91, NA, 27.25, 33.11, NA, 480.30, NA, 4.17, 17.89, 14.0, 7, 2.19, 1.22, 8.43, 3.10] }

I want to impute the missing values, but only with the mean of the bottom 25% of the values in the column (i.e. with 2.17, the average of 1.22, 2.19, 3.10). Is there a way to do this without having to escape outside the table and store the mean value as a variable?

Thanks!

[markwhiting]

I'm sure you have found a solution by now, but if not, the table.impute verb can do this for you. There are some example of it in use in the An Illustrated Guide to Arquero Verbs on Observable.