[英]Sum parts of column depending on conditional statement Matlab
我在matlab中有一個矩陣,如果其他列使用條件語句進行檢查,我想在其中對一列的值求和,然后我想以一種連貫的方式存儲求和后的值。
布局輸入表ListMax:
year Month day hour precipitation
1998 1 1 1 5
1998 1 2 2 7
1998 1 3 3 0
.... ... ... ... ...
布局輸出result_matrix:
year jan feb mar
1998 100 120 140
1999 90 110 130
... ... ... ...
我正在努力進行行初始化,檢查條件語句以及將值保存在輸出中的組合。
我有以下幾點注意事項,但不起作用:
result_matrix = zeros(15,12); %empty matrix 15 years, 12 months
year_number = 1998;
counting_years = 1;
counting_months = 1;
for (ii = 1: length(ListMax));
if ListMax(:,1) == year_number && ListMax(:,2) == counting_months;
result_matrix(counting_years, counting_months) = (sum(Listmax(:,5));
else % update month itirators
if counting_months < 12
counting_months = counting_months + 1;
else % end of year, set month count to 1
counting_months = 1;
end
year_number = year_number +1;
counting_years = counting_years + 1;
end
end
我可以看到這可能不是最直接的方法,但是目前我能想到的這種方法,現在只需要使它正常工作即可。 任何朝着正確方向的推動將不勝感激:)
您可以簡單地將accumarray
與兩accumarray
索引一起使用。
year Month day hour precipitation
1998 1 1 1 5
1998 1 2 2 7
1998 1 3 3 0
.... ... ... ... ...
例如,如果要根據年份和月份對降水總量求和,則可以將矩陣的第一兩列用作索引,將最后一列用作降水量。
sub = 1998 1 %Jan.1998
1998 1 %Jan.1998
1998 2 %Feb.1998
...
sub(:,1) = sub(:,1) - (min(sub(:,1))-1); %so the index for the year start at 1 and not 1998.
val = 6 %millimeter of precipitation on Jan.1998 day xxx
4 %millimeter of precipitation on Jan.1998 day xxx
7 %millimeter of precipitation on Feb.1998 day xxx
....
現在使用accumarray
:
result = accumarray(sub,val,[],@sum);
怎么樣(未試用):
year_start = 1998;
year_end = 2016;
result_matrix = zeros(year_end-year_start+1,12);
for year = year_start:year_end
for month = 1:12
rows = (ListMax(:,1)==year) & (ListMax(:,2)==month);
result_matrix(year-year_start+1,month) = sum(ListMax(find(rows),5));
end
end
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