how to find range of elements in each row of a matrix

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studentambitious
studentambitious 2017-2-20
编辑： soheilso 2018-5-4
i have a matrix of 8 x 5 and i want if there are at least two values in a row that lies between 6 and 8,then store the locations of those value else decrease the lower value from 6 to 5 and check if any value lies between 5 &8 else increase the upper value to 9 and check the values of a row lies between 7&9...I need to set the the range for each row and to store the location of the values in each row that lie in a specified range
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Walter Roberson
Walter Roberson 2017-2-20
This sounds like "make work" for a homework assignment, rather than something that would have real use??
studentambitious
studentambitious 2017-2-20
i m doing project where i need this thing to be done.. actually i have done a program where i have checked if the values lie between 7 & 8 and also find the locations of those values but i m not able to find the solution how to move the loop to increase and decrease the range for each row. shall i use switch/case or something else

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回答（3 个）

Image Analyst
Image Analyst 2017-2-20
If you want the range, why do it like that unusual way, which won't necessarily find the true range? Why not simply do this:
m = 9 * rand(5, 8) % Sample data
for row = 1 : 5
[minValue(row), colOfMin(row)] = min(m(row,:));
[maxValue(row), colOfMax(row)] = max(m(row,:));
end
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studentambitious
studentambitious 2017-2-20
actually range here is used for thresholding.. i need to check in each row if any or at least two values lies within a range of 7 & 8 If no then i have to check the values between range between 6(7-1) and 8 or if not then shift the higher range from 8 to 9.for each row the starting range will remain the same i.e. 7 & 8.

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Walter Roberson
Walter Roberson 2017-2-20
Let M be your matrix.
nrow = size(M,1);
location_to_remember = zeros(nrow, 1);
active_rows = 1 : nrow;
for thresh = [6 5 7; 8 8 9]
mask = M(active_rows, 1:end-1) >= thresh(1) & M(active_rows, 1:end-1) <= thresh(2) & ...
M(active_rows, 2:end) >= thresh(1) & M(active_rows, 2:end) <= thresh(2);
rows_with_matches = find( any(mask,2) );
for K = 1 : rows_with_matches
this_relative_row = rows_with_matches(K);
first_matchpair_in_row = find( mask(this_relative_row, :), 1, 'first' );
this_orig_row = active_rows(this_relative_row);
location_to_remember(this_orig_row) = first_matchpair_in_row;
end
active_rows(rows_with_matches) = [];
end
It is possible to vectorize the finding of the match pair instead of using the for K loop, but the code to do so would be less than clear.
soheilso
soheilso 2018-5-4
编辑：soheilso 2018-5-4
You are going to find the range of elements in A:
mins=min(A,[],2) %Gives you the minimum in each row.
maxs=max(A,[],2) %Gives you the maximum in each row.

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