how to sum data with condition

Question

Berk Gulmez 2019-10-9

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回答： Daniel M 2019-10-10

Hi everyone,

I have a dataset ;

x = [1 100; 1 101 ; 1 102; 2 109 ; 2 116 ; 2 118 ; 2 120 ; 3 103; 3 106]

I sorted data with respect to first column in ascending way while sorting second column again in ascending way.

Now, ı want to use functions those I prepared for this data with condition.

For instance, function 1 is used for [1 100] because it is first entry of value "1" in first column (calculation will be made with respect to column 2 value which is "100"). Then function 2 will continue until the end of "1" value in column 1.

when value "2" in column 1 enters, again function 1 calculates related value for "109" in column 2 and function2 will calculate other values for column2.

I cannot built correct loop for this calculation,

Thank you so much in advance.

Regards,

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Answer 1

John D'Errico 2019-10-9

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Sorry, but it is a really bad idea to have separate functions for each case.

Just pass in the the first column element as an argument to the function that does the computations. Then it is just a branch inside the function, or perhaps a switch/case.

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Berk Gulmez 2019-10-9

Unfortunaltey, I cannot seperate the functions becuase the calculation will be connected to previous row value. For instance,

y = [1 100; 1 101 ; 1 102];

for the first row, function1 answer is 100 (similar to first row)

then in the second row function2 gives 101-100 = 1 value until the first column value turn into "2".

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Answer 2

Daniel M 2019-10-10

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在 MATLAB Online 中打开

This is silly. But not difficult to implement.

x = [1 100; 1 101 ; 1 102; 2 109 ; 2 116 ; 2 118 ; 2 120 ; 3 103; 3 106];
y = x(:,1);
[~,startInds] = unique(y); % get the first index of each new number
y(setdiff(1:numel(y),b)) = 0; % set the other numbers to zero
for k = 1:size(x,1)
    if y(k)
        % code for function1(x(k,2));
    else
        % code for function2(x(k,2));
    end
end