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Create an array of two arrays in pairs without loops

A simple question here. I have arrays:

a = [ 600 746 8556 90456 ]
b = [ 684 864 8600 90500 ]

and I want to get:

output = [ a(1):b(1) a(2):b(2) a(3):b(3) a(4):b(4) ]

(or either [ a(1):b(1); a(2):b(2); a(3):b(3); a(4):b(4) ], I don't care)

I cannot figure out how to do this without using a loop, but I know that this should be a way.

Any idea?

early

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2 answers

Approach No. 1

Vectorizedwith the bsxfunability to disguise -

%// Get "extents" formed with each pair of "a" and "b" and max extent
ext = b-a
max_ext = max(ext)

%// Extend all a to max possible extent
allvals = bsxfun(@plus,a,[0:max_ext]')  %//'

%// Get mask of valid extensions and use it to have the final output
mask  = bsxfun(@le,[0:max_ext]',ext)  %//'
out  = allvals(mask).'

Approach # 2

Below is an cumsumapproach that should be more efficient in terms of memory and faster than the previous, listed bsxfunapproach and the arrayfunapproach in another answer . Here the code is

%// Get "extents" formed with each pair of "a" and "b"
ext = b-a;

%// Ignore cases when "a" might be greater than "b"
a = a(ext>=0);
b = b(ext>=0);
ext = b-a;

if numel(ext)>1

    %// Strategically place "differentiated" values from array,a
    idx = ones(sum(ext+1),1);
    idx([1 cumsum(ext(1:end-1)+1)+1]) = [a(1) diff(a)-ext(1:end-1)];

    %// Perform cumulative summation to have the final output
    out = cumsum(idx)

else %// Leftover cases when there are one or no valid boundaries:(a->b)
    out = a:b
end

Run Example -

>> a
a =
     6    12    43
>> b
b =
     8    17    43
>> out
out =
     6     7     8    12    13    14    15    16    17    43
+8
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, arrayfun, cell2mat :

output = cell2mat(arrayfun(@(start, stop) start:stop, a, b, 'uni', 0))

: arrayfun a b, . , 'UniformOutput', false ( 'uni', 0), arrayfun . , cell2mat, .

:

>> a = [10, 20, 40];
>> b = [13, 22, 45];
>> output = cell2mat(arrayfun(@(start, stop) start:stop, a, b, 'uni', 0))
output =
    10    11    12    13    20    21    22    40    41    42    43    44    45
+7

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