R help - Mar 2011 - using lapply

I have a function with the follow signare:

apply.strategy(instr, strat)

where instr and strat are both objects of classes instrument and strategy
respectively.

I want to apply this function to a list that holds objects of the class
instrument.

Currently I am doing this by explicit looping:

for(i in length(instr.list) ) {
    apply.strategy(instr.list[[i]], my.strat)
}

Is it possible to achieve this task by using one of the built in functions
in R? I have looked at lapply but can't quite figure out how to pass the
arguments.

What would be the performance implications of one method vs. the other?

Thanks,
Kushan

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On reply to the post
http://r.789695.n4.nabble.com/using-lapply-td3345268.html

Dear Kushan, this may be a good start:

## assuming 'instr.list' is  your list object and you are applying
my.strat() function on each element of that list, you can use lapply
function as
lapply(instr.list, function(x) return(my.strat(x)))

Here resulting element will again be another list with length is same as the
length of your original list 'instr.list.'

Instead if the returned object for my.strat() function is a single number
then you might want to create a vector instead list, in that case just use
'sapply'

HTH

Arun,

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On 10.03.2011 03:46, Kushan Thakkar wrote:
> I have a function with the follow signare:
>
> apply.strategy(instr, strat)
>
> where instr and strat are both objects of classes instrument and strategy
> respectively.
>
> I want to apply this function to a list that holds objects of the class
> instrument.
>
> Currently I am doing this by explicit looping:
>
> for(i in length(instr.list) ) {
>      apply.strategy(instr.list[[i]], my.strat)
> }

lapply(instr.list, apply.strategy, strat=mystrat)

Uwe Ligges


>
> Is it possible to achieve this task by using one of the built in functions
> in R? I have looked at lapply but can't quite figure out how to pass
the
> arguments.
>
> What would be the performance implications of one method vs. the other?
>
> Thanks,
> Kushan
>
> 	[[alternative HTML version deleted]]
>
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