Help with indexing problem.
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Hi, I would like help with this indexing problem. I have a 5x3 matrix called 'P_table' and I want to find the sum for all the rows and subtract the maximum value of each row. Also I would like to know how to use the index to check which column the maximum value is for each row in a variable 'column', if a specific column does not contain any maximum value then all the elements in that column are zeroed. Thanks.
for ite=1:length(P_table)
P_max = find(max(P_table(ite,:),[],2));
P_max = P_table(P_max);
P_sum=sum(P_table,2)-P_max;
end
For example if
P_table=
0.2432 0.3687 0.2879
0.2225 0.5833 0.3497
0.2485 0.4484 0.4167
0.2859 0.2019 0.2720
1.0000 0.6313 0.4401
Then column=
2
2
2
1
1
Since column 3 does not contain any of the maximum values it is zeroed.
P_table=
0.2432 0.3687 0
0.2225 0.5833 0
0.2485 0.4484 0
0.2859 0.2019 0
1.0000 0.6313 0
P_sum=
0.2432
0.2225
0.2485
0.2019
0.6313
采纳的回答
Image Analyst
2015-4-29
Instead of a for loop, use the appropriate input and output arguments of sum() and max():
P_table=[...
0.2432 0.3687 0.2879
0.2225 0.3497 0.5833
0.2485 0.4484 0.4167
0.2859 0.2019 0.2720
1.0000 0.6313 0.4401]
% Vectorized approach:
% Find sums of rows, going across all columns.
rowSums = sum(P_table, 2)
% Find maximas in each row and the column where it occurs.
[rowMaxima, columsOfMaxima] = max(P_table, [], 2)
% Compute the difference.
P_sum = rowSums - rowMaxima
It gives you exactly what you showed.
3 个评论
Image Analyst
2015-4-29
New code to delete columns with no max in them:
P_table=[...
0.2432 0.3687 0.2879
0.2225 0.3497 0.5833
0.2485 0.4484 0.4167
0.2859 0.2019 0.2720
1.0000 0.6313 0.4401]
% Vectorized approach:
% Find sums of rows, going across all columns.
rowSums = sum(P_table, 2)
% Find maximas in each row and the column where it occurs.
[rowMaxima, columsOfMaxima] = max(P_table, [], 2)
% Compute the difference.
P_sum = rowSums - rowMaxima
% Get rid of any columns that don't contain at least one maximum
[rows, columns] = size(P_table)
columnsToDelete = setdiff(1:columns, unique(columsOfMaxima))
if ~isempty(columnsToDelete)
% Delete those columns
P_table(:, columnsToDelete) = [];
end
If this answers the question, can you mark it as "Accepted"?
ajk1
2015-4-29
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