Convert to serial using only year and month (no day)

Is there a way to convert from matrix A (5x3) where the first element is year and the second element is month (no day element) to a serial number in matrix B (5x2)?

A=...
[2013 12 0.6;
2013 12 0.8;
2014 1 0.5;
2014 2 0.1;
2014 2 0.7]

Answer should be:

B=...
[serial1 0.6;
serial1 0.8;
serial2 0.5;
serial3 0.1;
serial3 0.7]

Where serial1 is a number for 'Dec-2013' and so on. Thanks

Answer 1

[Guillaume]

A date number (serial) has to have a day (and hour, minutes, seconds, if not given, the default is 0:0:0), so use the first of the month for example:

A = [2013 12 0.6; 2013 12 0.8; 2014 1 0.5; 2014 2 0.1; 2014 2 0.7];
B = [datenum(A(:, 1), A(:, 2), 1) A(:, 3)]

Answer 2

[dpb]

Sure, just use an arbitrary day -- '1' would be a logical choice although you could choose any day within the month.

B=[datenum(A(:,1), A(:,2), 1) A(:,3)];