[英]Sum parts of column depending on conditional statement Matlab
我在matlab中有一个矩阵,如果其他列使用条件语句进行检查,我想在其中对一列的值求和,然后我想以一种连贯的方式存储求和后的值。
布局输入表ListMax:
year Month day hour precipitation
1998 1 1 1 5
1998 1 2 2 7
1998 1 3 3 0
.... ... ... ... ...
布局输出result_matrix:
year jan feb mar
1998 100 120 140
1999 90 110 130
... ... ... ...
我正在努力进行行初始化,检查条件语句以及将值保存在输出中的组合。
我有以下几点注意事项,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
我可以看到这可能不是最直接的方法,但是目前我能想到的这种方法,现在只需要使它正常工作即可。 任何朝着正确方向的推动将不胜感激:)
您可以简单地将accumarray
与两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,如果要根据年份和月份对降水总量求和,则可以将矩阵的第一两列用作索引,将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
....
现在使用accumarray
:
result = accumarray(sub,val,[],@sum);
怎么样(未试用):
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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