[R] How to modify data frame stored in a list

[Bert Gunter]

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-- Bert



Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Mon, Jun 18, 2018 at 2:58 PM, Honkit Wong <stephen66 using gmail.com> wrote:

> Thanks!
> Why have to add “x” at the end of function, which was what I missed.
>
> On Jun 18, 2018, at 2:53 PM, Bert Gunter <bgunter.4567 using gmail.com> wrote:
>
> It depends on whether you wish to refer to the column to be logged by name
> or index.
>
> Reprex:
>
> set.seed(1234)
> dat <- lapply(1:3, function(i)data.frame(a = runif(5), b =
> sample(letters,5)))
>
> ## by numerical index of column
> d <- lapply(dat,function(x){x[,"logged"]<- log10(x[,1]); x})
>
> ## by name of column
> dd <- lapply(dat,function(x){x[,"logged"]<- log10(x[,"a"]); x})
>
> There are also slight variations on how you can do the "[" indexing that
> others may post.
> Note that you have to return the modified data frame in the function.
>
> Cheers,
> Bert
>
>
>
>
>
>
> Bert Gunter
>
> "The trouble with having an open mind is that people keep coming along and
> sticking things into it."
> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>
> On Mon, Jun 18, 2018 at 1:46 PM, Honkit Wong <stephen66 using gmail.com> wrote:
>
>> Dear R community,
>> I have a question seems very simple but have trouble to do it.
>> I have a list which stores many data frames. Now, I want to perform log10
>> on one column in each data frame in the list and save the value as a new
>> column back to the original data frame in the list. How do I quickly do
>> that with lapply function ?
>>
>> Many thanks.
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>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>

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