First of all I'd like to thank Marco for his great answer to Martin's question. I am fairly new to Mathematica and really learned a lot from his examples.

Here's another suggestion, which (similar to Marco's third example) makes use of the Query function for datasets.

Dataset[families]["smith", "ratios", All, MapAt[2 # &, "height"]]

What's different is mainly the use of the operator form of the MapAt function. The advantage is improved readability and it retains the dataset structure consisting of a list of associations, which facilitates use of the output for further queries if so desired.

Cheers, Eric

Hi,

this could work:

Dataset[{2*#["height"], #["weight"]} & /@ families["smith", "ratios"]]

If you want to keep the dataset structure intact, this works:

Dataset[<|"height" -> 2*#["height"], "weight" -> #["weight"]|> & /@ families["smith", "ratios"]]

You can also use Query

Query[All, {2 #["height"] &, "weight"}]@Dataset[families["smith", "ratios"]]

Cheers,

Marco