MATLAB: Problem with coding cumsum statement

cumsum error

Hi all, I am really stuck with this one ! I am trying to tell matlab to calculate at which day the cumulative rainfall reaches 8mm I should only use vectorisation for this code. 2 issues here:
1- I keep getting this error: "CUMSUM supports only numerical or logical inputs." If I create the arrays manually cumsum seems to work, but if I call it from a table, it give me the above error. Does this mean, I need to create the arrays manually?
2- If if I manage to get it to work, how on Earth do I tell matlab to keep adding the rainfall values until it reaches 8mm then exit and display on which day the goal was reached without using loop ?? I have attached the file and a draft of my code below: Any help would be highly appreciated !
Many thanks in advance !
    RF_tbl=readtable('Test_data1.csv');
    date=[1:31]; % I tried first to call the date column from the table but that caused a problem.
    RF_V= RF_tbl(6:36,5); %This calls the rainfall column from the table, which I need to calculate
    if cumsum(RF_V)<=8
        'continue'
    else
        'exit and display the date on which the goal reached' % This is not the code, this is just to explain what I need to achieve.
    end

Best Answer

Your data are stored as cells, not as matrix. Your values are also strings and need to be cast to numbers first. This code might work for you (it will throw an error if the 8mm rainfall are not reached within the month):
data=readtable('Test_data1.csv');
mysum=cumsum(str2double(data{6:end,5}));
idx=find(mysum>=8,1);
date=data{idx+6,2}
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