Select from data table as list in R

Asked Apr 15 '18 at 18:56

Active Apr 15 '18 at 19:17

Viewed 220 times

I am trying to select a list from a data table and apply a function. Finally I want the result as a column of the data table.. Following is an example of what i am trying to do ...

I tried something like this :

dt <- dt[, value:=f(V3) , by=list(V1)]

Data table:

Result :

V1 Value
1  f(list(40,22,36))
2  f(list(11,8,20,18))
3  f(list(...))

edited Apr 15 '18 at 19:17

Jaap

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asked Apr 15 '18 at 18:56

noname

Write `?apply` in the r console. – Andreas Storvik Strauman Apr 15 '18 at 18:57
On my phone here, but something like `apply(data$V3, f)` should work. – Andreas Storvik Strauman Apr 15 '18 at 18:58
1

If the `f` is taking argument as a `list`, then `dt[, .(value = f(list(V3))), V1]` and if you need as a column `dt[, value := f(list(V3)), V1]` – akrun Apr 15 '18 at 18:58
Related / possible duplicate: [*Collapse / concatenate / aggregate a column to a single comma separated string within each group*](https://stackoverflow.com/q/15933958/2204410) – Jaap Apr 15 '18 at 19:18
1

@akrun Thank you, your suggestions worked well :) – noname Apr 17 '18 at 13:18

Select from data table as list in R

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