Monthly sum function with nansum not being used correctly

Question

Augusto Gabriel da Costa Pereira 2022-11-8

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1846328-monthly-sum-function-with-nansum-not-being-used-correctly

评论： Mathieu NOE 2022-11-9

INMET_Diario.mat

I use the function below to perform the monthly precipitation accumulator, however, when there are days without NaN measurements in a given month, the result for that month is zero. But this result is wrong, the correct series for this month is NaN and not zero.

Another problem seen in the function is the result of months. From January 2000 to December 2020 there are 252 months. when I use the function, the result is only 251 months, that is, one month to go

Below is:

1 - the function used for the monthly sum.

2 - rainfall data, in column 1 the days of the year and in columns 2, 3, 4 and 5 the rainfall (INMET_Diario.mat);

function Y = monthly_sum(time_X,X)
[l,c] = size(X);
grp = [];
for y = 2000:2020 % Change period here
    for m = 1:12
        grp = [grp datenum(y,m,1)];
    end
end
    
X_hour = zeros(length(grp)-1,c);
for i = 1:length(grp)-1
        if(mod(i,500)==0)
                disp(i)
        end
        for j = 1:c
            X_hour(i,j) = nansum(X(time_X>=grp(i) & time_X<grp(i+1),j)); 
        end
end
Y = [grp(1:length(grp)-1)', X_hour];

Best Regards,

AP

3 个评论
显示 1更早的评论隐藏 1更早的评论

Augusto Gabriel da Costa Pereira 2022-11-8

If my goal is to AVERAGE, replace @sum with @mean on the last line?

Mathieu NOE 2022-11-9

在 MATLAB Online 中打开

yes that works also

A = [19260702    0.026   0.000   NaN 1.175
     19260705    0.036   0.002   NaN 2.175
     19260715    0.044   0.003   NaN 3.175
     19260816    0.042   0.007   NaN 25.928];
% Matrix to table conversion
T = array2table(A,'VariableNames',{'DATE','S1','S2','S3','S4'});
% We add a new column "month"
T.MONTH = floor(T.DATE/100);
% varfun can apply a custom function to your table and group the result according 
% to one (or more) variable(s)
Result_sum = varfun(@sum,T,'InputVariables',{'S1','S2','S3','S4'},'GroupingVariables','MONTH')
Result_mean = varfun(@mean,T,'InputVariables',{'S1','S2','S3','S4'},'GroupingVariables','MONTH')

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Answer 1

Jan 2022-11-8

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1846328-monthly-sum-function-with-nansum-not-being-used-correctly#answer_1094273

编辑：Jan 2022-11-8

在 MATLAB Online 中打开

function Y = monthly_sum(T, X)
grp = [datenum(2000, 1:252, 1), Inf];
ngrp = numel(grp) - 1;
c = size(X, 2);
X_hour = nan(ngrp, c);
for i = 1:ngrp
    for j = 1:c
        TX = X(T >= grp(i) & T < grp(i+1), j);
        if ~isempty(TX)
           X_hour(i,j) = nansum(TX); 
        end
    end
end
Y = [grp(1:ngrp).', X_hour];
end