Re: How to apply a list of functions
- To: mathgroup at smc.vnet.net
- Subject: [mg112886] Re: How to apply a list of functions
- From: "Vincent N. Virgilio" <virgilio at ieee.org>
- Date: Tue, 5 Oct 2010 05:32:29 -0400 (EDT)
Leonid,
I notice that Inner/Compose is a little fragile if x is, say, a list of
matrices, and the goal is to apply each f to each whole matrix.
MapThread/Compose handles that transparently.
Thanks again,
Vince
On Mon, Oct 4, 2010 at 1:07 PM, Leonid Shifrin <lshifr at gmail.com> wrote:
> Hi Vince,
>
> First, you could use Compose in your code - perhaps it is a little faster:
>
> In[2]:= MapThread[Compose,{{f1,f2,f3},{x1,x2,x3}}]
>
> Out[2]= {f1[x1],f2[x2],f3[x3]}
>
> Using Inner can be a bit faster still:
>
> In[4]:= Inner[Compose,{f1,f2,f3},{x1,x2,x3},List]
>
> Out[4]= {f1[x1],f2[x2],f3[x3]}
>
> In most cases, you probably won't see the difference in performance, unless
> your functions
> do very little and you have lots of them.
>
> Regards,
> Leonid
>
>
>
>
> On Mon, Oct 4, 2010 at 2:06 PM, Vince Virgilio <blueschi at gmail.com> wrote:
>
>> On Oct 3, 3:39 am, Sam Takoy <sam.ta... at yahoo.com> wrote:
>> > Hi,
>> >
>> > As a follow up to my question about apply {Sin, Cos} to x, I came up
>> > with the tasteless
>> >
>> > Map[Apply[#, {x}] &, {Sin, Cos}]
>> >
>> > but I expect that the pros in this ng will be able to improve upon it.
>> >
>> > Thanks,
>> >
>> > Sam
>>
>> Tangentially,
>>
>> I've always wondered if there was a better way to apply a list of
>> functions to a list of arguments. Here's how I do it, where f and x
>> are the respective lists.
>>
>> MapThread[#1@#2 &, {f, x}]
>>
>> Seems performant.
>>
>> Anyone?
>>
>> Vince
>>
>>
>