derive can not handle string?

[winner106]

name	style	brewery_id	abv	ibu	test
#002 American I.P.A.	American IPA	211	0.071	60
#004 Session I.P.A.	American IPA	211	0.048	38
#9	Fruit / Vegetable Beer	303	0.051	20
077XX	American Double / Imperial IPA	222	0.078	80
113 IPA	American IPA	371	0.070	113
12th Round	American Strong Ale	376	0.076	78
13 Rebels ESB	Extra Special / Strong Bitter (ESB)	433	0.052	42
1327 Pod's ESB	Extra Special / Strong Bitter (ESB)	380	0.056	37
14° ESB	Extra Special / Strong Bitter (ESB)	75	0.056	32
1554 Black Lager	Euro Dark Lager	82	0.056	21

beers.derive({test: (d) => d['style'].split(' ')[0]})

can not add new text column

[jcmkk3]

Try to use the op functions instead of methods.

beers.derive({test: (d) => op.split(d.style, '  ')[0]})

https://uwdata.github.io/arquero/api/op#split

[jheer]

@jcmkk3 is right. As described in the documentation, by default Arquero will rewrite functions to optimize data access paths. To make this safe and predictable, arbitrary object-bound methods can not be used.

To sidestep this within a derive (and also allow access to closure variables), you can preserve a normal function by using aq.escape(func) to wrap the function. However, this will opt out of any optimization, potentially causing reduced performance. But if your data is not particularly large you probably won't notice an issue.