How to sort a matrix into groups according to the times at which they occur?

Hello,

I have a matrix called pRatio1 which has dimensions (4140,2). The first column of the matrix relates to time and the second column of the matrix relates to a data observation at each corresponding time. The data observations are random and not sampled at a set rate.

The time is of form 0.00 represents midnight, 0.25 quarter past midnight, 0.5 half past midnight all the way up to 23.99.

What I want to do is write a piece of code that would split the data into five minute periods. So, for example, all data that falls between midnight and five past midnight would become part of a new matrix.

Any ideas of how to do this?

Thanks

Rory

[dpb]

If you mean the above literally, then it's simply

y=x(iswithin(x(:,1),0,5/24),:);  % include the timestamp, too

y=x(iswithin(x(:,1),0,5/24),2);  % just the data instead

The question is, do you care/need the day info or just that it's during the desired fraction of a day when collected irrespective of day?

iswithin is my helper function

function flg=iswithin(x,lo,hi)
% returns T for values within range of input
% SYNTAX:
%  [log] = iswithin(x,lo,hi)
%      returns T for x between lo and hi values, inclusive
%
    flg= (x>=lo) & (x<=hi);

which makes writing such logic expressions easier by hiding the complexity of the test at a lower level.