Convert vector of datenum values to datetime values

Question

Kyle Reagan 2017-6-12

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回答： Peter Perkins 2017-6-20

The first column of a 3x2 matrix is datenum values. How do I convert each element to datetime? It looks as follows:

b = [736848]    'words'
    [736849]    'words'
    [736852]    'words'

I want to convert b(:,1) to either datestr or datetime form such that each row looks like

b = 02-Jun-2017.

Can anybody help me do this? I get an error if I try doing

datestr((b:,1)) or datetime(b(:,1))

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Answer 1

Stephen23 2017-6-12

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编辑：Stephen23 2017-6-12

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It seems that b is a cell array, and each cell in the first column contains one scalar datenum. You can use cell2mat to convert the first column of cells into a numeric vector:

vec = cell2mat(b(:,1));
datestr(vec)
datetime(vec)

Or vertcat:

vec = vertcat(b{:,1});

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Kyle Reagan 2017-6-12

Thanks, Stephen! It works just as anticipated.

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Answer 2

Peter Perkins 2017-6-20

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There's actually a direct conversion, once you lose the cell array:

vec = cell2mat(b(:,1));
datetime(vec,'ConvertFrom','datenum')

This is more than a convenience, there is some numeric magic to try to mitigate the fact that datenum uses a somewhat awkward unit of time, i.e. 1 day.