How to apply a cell array of function handles to an array of double

I've got code:

array_double = randi (3,3)
cell_array_fuction_handles ={@(x)x*2 @(x)x*4 @(x)x*6};

for k = 1:length (array_double)
array_double(k,:) = arrayfun (cell_array_fuction_handles{k}, array_double(k,:));
end

array_double

Is there any way to replace for-loop with a vector function?

Thanks!

Answer 1

[Andrei Bobrov]

In your case:

out = array_double.*(2:2:6)';

General case:

out = arrayfun(@(x,y)cell_array_fuction_handles{x}(y),...
                                                repmat((1:3)',1,3),array_double);

[madhan ravi]

arrayfun() is slower than a loop

[Artur Suglob]

Thanks a lot!

Actually it is somehow slower.

If I understand right, this code uses "repmat" matrix to index through function handles array and apply it (function handle) to each element of double array. So it actually works as nested for-for loop.

So I've tested some variants:

array_double = randi (100,3);
cell_array_fuction_handles ={@(x)x*2 @(x)x*4 @(x)x*6};
time1=0;array_double1=array_double;
time2=0;array_double2=array_double;
time3=0;array_double3=array_double;
time4=0;array_double4=array_double;

for kk =1:1000000
%%for loop + direct f(x)
tic
for k = 1:length (cell_array_fuction_handles)
    array_double1(k,:) = cell_array_fuction_handles{k}(array_double(k,:));
end
time1=toc+time1;
%% for-for nested loop
tic
for k = 1:length (cell_array_fuction_handles)
    for j = 1:length (array_double)
    array_double2(k,j) = cell_array_fuction_handles{k}(array_double(k,j));
    end
end
time2=toc+time2;
   
%% for loop + arrayfun     
tic
for k = 1:length (cell_array_fuction_handles)
array_double3(k,:) = arrayfun (cell_array_fuction_handles{k}, array_double(k,:));
end
time3=toc+time3;
%% only arrayfun
tic
array_double4 = arrayfun(@(x,y)cell_array_fuction_handles{x}(y),repmat((1:3)',1,3),array_double);
time4=toc+time4;

end

time1
time2
time3
time4

So it looks like the first is the best.

[madhan ravi]

Well that is what I mentioned!!

[Artur Suglob]

Thanks!