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

[Honkit Wong]

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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