Re: Apply Polyval to Array

[Dmitri A. Sergatskov]

On Sun, Jun 12, 2016 at 10:25 PM, Doug Stewart <address@hidden> wrote:

On Sun, Jun 12, 2016 at 10:03 PM, Thomas D. Dean <address@hidden> wrote:

I want to vectorize this:

p1 = [1,2,3;4,5,6;7,8,9];
for idx=1:3
  polyval(p1(idx,:),0)
endfor

cellfun("polyval",{p1},{[0;0;0]}); ## fails
arrayfun("polyval",p1,0 "UniformOutput",false)); ## wrong
arrayfun("polyval",p1,zeros(3,3), "UniformOutput",false); ## wrong

Tom Dean

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does this help

p1 = [1,2,3;4,5,6;7,8,9];

t=[1 2 3]

f=@(t) polyval(p1(t,:),0)

arrayfun(f,t)

​it works, but hardly faster than the loop on my computer.

​>> p1=rand(1000);
>> tic; for idx=1:1000; polyval(p1(idx,:),0) ; endfor; toc
Elapsed time is 4.96287 seconds.
>> t=1:1000;
>> f=@(t) polyval(p1(t,:),0)
f =

@(t) polyval (p1 (t, :), 0)

>> tic; arrayfun(f,t); toc
Elapsed time is 4.82834 seconds.

​Dmitri.
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​