for loop and indexing a matrix help

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Aroi Mehu
Aroi Mehu 2020-4-23
评论： Aroi Mehu 2020-4-23
Trying to make a function that if i input a matrix(x) and its conditions(cond), (x,cond)- it will resutun the index(row numders) that meet the conditions, as a vector. Any good examples of how this can be executed. Or if matlab has any helpful docs that can help?

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回答（1 个）

KSSV
KSSV 2020-4-23
A = rand(5) ;
idx = A>0.7 ; % indices greater than 0.7
find(idx)
A(idx)
idx = A<0.5 ; % indices less than 0.5
find(idx)
A(idx)
idx = A>0.3 & A<0.7 ; % indices greater than 0.3 and less than 0.7
find(idx)
A(idx)
  1 个评论
Aroi Mehu
Aroi Mehu 2020-4-23
that makes sense but how about using for loops? For example the function below
Inputs for example :
x = [1 2 3 4; 70 62 45 65; 23 17 19 20; 51 34 56 72];
conditions = [60 20 50];
ind = avada(x,cond)
function ind = avada(x,cond)
y = false(size(x)-[1 0]); %iNITIALIZE Y
for i=1:size(x,2)-1 % Run for loop for 3 times i.e. 1 less than 4
y(i,:) = x(i+1,:)>=cond(i);% condition,all values greater than equal to cond will be true
end
ind = x(1,sum(y)== (size(x,2)-1)); %
end
those inputs give me a correct result, however,
when i try to input x =[1 2 3 4 5 6 7 8 9 10; 70 70 62 45 65 88 69 10 56 92; 23 17 19 20 19 17 20 21 23 24; 51 34 56 72 77 88 99 49 50 70] with the same conditions, it says
Index in position 1 exceeds array bounds (must not exceed 4).

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