How can I merge vector elements into a single number of type double?

Asked by Lazaros Ioakeimidis on 4 Feb 2019

Latest activity Commented on by Guillaume on 5 Feb 2019

Accepted Answer by Guillaume

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Hello,

How can I transform this vector:

v=[1 2 3]

into this scalar of type double?:

k=123

Thank you,

Lazaros.

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3 Answers

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Answer by Guillaume on 4 Feb 2019

Edited by Guillaume on 4 Feb 2019

Accepted Answer

k = polyval(v, 10)

is probably the easiest.

This assume of course that each element of v is an integer in the range [0-9].

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Answer by Jan on 4 Feb 2019

Edited by Jan on 4 Feb 2019

x = [1,2,3];
d = x * 10 .^ (numel(x)-1:-1:0).'   % dot product

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Answer by YT on 4 Feb 2019

Edited by YT on 4 Feb 2019

Something like this?

A = [1 2 3];
joined = str2num(strjoin(num2cell(num2str(A(:))),''));
%>> joined = 123 (type double)

There are probably some more elegant solutions, but this is what I came up with for now.

3 Comments

Guillaume on 4 Feb 2019

If you were going to go through strings and back, this would be simpler and faster:

str2num(char(A + '0'))

However, conversion of numbers to/from strings are slow (compared to just doing maths)

YT on 4 Feb 2019

Looks much better. Thanks, learned something new today. The only downside to this is that, like you stated in your polyval solution, that this also only works correctly for positive integers.

Guillaume on 5 Feb 2019

Indeed but that is most likely the case I assume.

A simpler, yet more generic solution, using number->string->number conversion:

str2num(strjoin(compose('%d', A), ''))

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Lazaros Ioakeimidis (view profile)