MATLAB如何在IF语句中使用FIND函数

Question

这个问题与我如何在MATLAB中合并这些数据有关？

如何在IF语句中使用FIND函数？ 例如，如果我有此数据：

20  10  1
20  11  1
20  15  1
23  10  1
23  10  1
23  12  0

规则1：第3列的数据必须为1。

规则2：如果n是第1列的当前索引，则如果n等于n-1列的n-1 （20 = 20），则将索引n和n-1的第2列的数据合并。

20  21  0
20  15  0
20  0   0
23  20  0
23  0   0
23  12  0

编辑：

fid=fopen('data.txt');
A=textscan(fid,'%f%f%f');
fclose(fid);
in = cell2mat(A)'; %'# fix for SO formatting - Jonas

%# rows2mergeFrom are the rows where the second row equals the first row of col 1
%# and where the third column is 1. rows2mergeInto indicates the rows from which  the
%# values of the following rows should be added
rows2mergeFrom = find(in(2:end,1) == in(1:end-1,1) & in(2:end,3) == 1) + 1;

out = in;
out(rows2mergeFrom-1,2) = out(rows2mergeFrom-1,2) + out(rows2mergeFrom,2);

%# data that has been shifted up gets subtracted from the 'rows2mergeFrom'-rows
out(rows2mergeFrom,2) = out(rows2mergeFrom,2) - in(rows2mergeFrom,2);

%# remove the ones in the third column from any row that has been involved in a 
%# merge operation
out([rows2mergeFrom;rows2mergeFrom-1],3) = 0

fid = fopen('newData.txt','wt');  
format short g;
fprintf(fid,'%g\t %g\t %g\n',out);  %'# Write the data to the file
fclose(fid);  

Answer 1

无需if语句。 您需要一个逻辑数组，该数组允许find提取要合并的行的行索引。

更新以符合新规则

in = [20  10  1
20  11  1
20  15  1
23  10  1
23  10  1
23  12  0];

%# rows2mergeFrom are the rows where the second row equals the first row of col 1
%# and where the third column is 1. rows2mergeInto indicates the rows from which  the
%# values of the following rows should be added
rows2mergeFrom = find(in(2:end,1) == in(1:end-1,1) & in(2:end,3) == 1) + 1;

out = in;
out(rows2mergeFrom-1,2) = out(rows2mergeFrom-1,2) + out(rows2mergeFrom,2);

%# data that has been shifted up gets subtracted from the 'rows2mergeFrom'-rows
out(rows2mergeFrom,2) = out(rows2mergeFrom,2) - in(rows2mergeFrom,2);

%# remove the ones in the third column from any row that has been involved in a 
%# merge operation
out([rows2mergeFrom;rows2mergeFrom-1],3) = 0

out =
20    21     0
20    15     0
20     0     0
23    20     0
23     0     0
23    12     0

Answer 2

据我所知，您不需要使用find或if。 您只需要逻辑索引。

如果我正确理解了您的问题，Amro会指出您的输出与您对逻辑的描述不匹配是正确的。 尝试以下脚本：

m = [20  10  0; ...
     20  11  0; ...
     20  15  1; ...
     23  10  1; ...
     23  10  1];
merge = (m(1:end-1, 1) == m(2:end, 1)) & (m(2:end,3) == 1)
mnew = m(2:end, :);
madd = m(1:end-1,2) + m(2:end,2);
mnew(merge, 2) = madd(merge);
mnew = [m(1,:); mnew]