how to sum different rows within a column
显示 更早的评论
I have 2 columns with 3101 values and i want to add the row 1&2 then row 2&3, 3&4 and so on..
I want to execute this calculation for the entire column with a cummulative sum
p=0.5*(column1(row1+row2))*column2(row2-row1)
the next row should be = 0.5*(column1(row2+row3))*column2(row3-row2) + p
How can I select 2 row values in the same column with the output created in a different column?
Thanks in advance
采纳的回答
One approach would be to create the third column independently and then concatenate it at the end —
A = randi(9,10,2);
p = 0;
for k = 1:size(A,1)-1
v(k,:) = (A(k,1)+A(k+1,1))/2 * (A(k+1,2)-A(k,2)) + p;
p = v(k);
end
A(:,3) = [NaN; v]
.
更多回答（1 个）
Image Analyst
2022-3-31
"to add the row 1&2 then row 2&3, 3&4 and so on.." you can use conv:
kernel = [1;1];
sums = conv(column1, kernel, 'valid');
kernel = [-1; 1];
diffs = conv(column2, kernel, 'valid');
If you want it multiplied by 0.5 and cumulatively summed, you can .....
Well actually I think Star's for loop approach is much simpler to do and understand than my vectorized approach so just go with that.
类别
在 帮助中心 和 File Exchange 中查找有关 Creating and Concatenating Matrices 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
