Manipulate time series matrix

I have a time series matrix like this:

Yr Month Day Hour Min Precipitation-rate

1997 01 01 00 00 0.5
1997 01 01 00 15 0.2
1997 01 01 00 30 0.0
1997 01 01 00 45 0.0
1997 01 01 01 00 0.0
1997 01 01 01 15 0.0
1997 01 01 01 30 0.1
1997 01 01 01 45 0.3
1997 01 01 02 00 0.5

I need hourly data, so I want to sum precipitation values for each full hour, getting this:

1997 01 01 00 00 0.7
1997 01 01 01 00 0.4

There's a practical way to do that on Matlab?

Tks

Answer 1

[Azzi Abdelmalek]

M=[1997 01 01 00 00 0.5
1997 01 01 00 15 0.2
1997 01 01 00 30 0.0
1997 01 01 00 45 0.0
1997 01 01 01 00 0.0
1997 01 01 01 15 0.0
1997 01 01 01 30 0.1
1997 01 01 01 45 0.3
1997 01 01 02 00 0.5]
[ii,jj,kk]=unique(M(:,1:4),'rows')
out=[ii accumarray(kk,M(:,6))]