How to consolidate rows with same value, while adding their cells?

I have NOAA climate data reported every 15 minutes and need to consolidate it into daily info. I want to add cells at the end of a row together that have the same date, and make a new matrix with the 'summed' and consolidated info. Here is a rough example of what I want to do:

FROM:

[date, precip

2/1,    4

2/1,    5

2/1,    6

2/2,    2

2/2,    3

2/2,    1

2/2,    4]

TO:

[date, precip

2/1,    15

2/2,    10]

Answer 1

[Doug Hull]

clear

d = {'date', 'precip'; '2/1', 4; '2/1', 5; '2/1', 6; '2/2', 2; '2/2', 3; '2/2', 1; '2/2',4}

dates  = {d{2:end,1}};
amount = [d{2:end,2}];

[uniqueDates, firstInd, allInd] = unique(dates);

for i = 1:numel(firstInd)
    totalRain(i) = sum(amount(allInd == i));
end

disp(uniqueDates)
disp(totalRain)

[Azzi Abdelmalek]

Ethan commented

Thanks a bunch! working like a charm.

Answer 2

[Azzi Abdelmalek]

s = { '2/1', 4; '2/1', 5; '2/1', 6; '2/2', 2; '2/2', 3; '2/2', 1; '2/2',4}
[a,b,c]=unique(s(:,1),'stable')
out=[a num2cell(accumarray(c,cell2mat(s(:,2))))]