matlab - Logical indexing creates row instead of column -


i failing understand behaviour of matlab i've discovered. here code:

ix = logical([1; 0; 1]); value = [2; 2; 2]; newvalue(ix) = value(ix)

it outputs 

2 0 2

while expect

2 0 2

i can “correct” adding newvalue = nan(size(value)) before code. understand why matlab creates row column vectors.

it behavior because when create array using indexing: a(1) = 2; a(2) = 3;, matlab (and octave) create row (a=[2, 3]). , when use logical indexing use method. in case matlab executes

newvalue(1) = value(1);  newvalue(3) = value(3);

but @irreducible says, can avoid pre-allocating newvalue

and can obtain same results without using logical indexing with:

ix = [1; 0; 1]; value = [2; 2; 2]; newvalue = value.*ix;

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