How can I do matrix indexing
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I want to select 3 elements from the matrix C, one element from each column, the selecting will be regarding to the maximum value in in each column in matrix f.
C=
41.0875 66.4048 31.5374
84.3670 25.9733 73.1052
68.8608 99.4798 75.5581
the vector needed like this [ 68.8608 66.4048 73.1052 ]
f=
1.0027 0.9766 1.2106
0.4001 0.5136 1.8174
1.5451 0.9488 0.8571
and because this values and positions are subject to change randomly
any help will be very thankful
採用された回答
Stephen23
2019 年 2 月 8 日
編集済み: Stephen23
2019 年 2 月 8 日
A simple and reliable solution using linear indexing:
>> f = [1,22,333;4,33,111;1,4,33]
f =
1 22 333
4 33 111
1 4 33
>> C = [41.0875,66.4048,31.5374;84.3670,25.9733,73.1052;68.8608,99.4798,75.5581]
C =
41.087 66.405 31.537
84.367 25.973 73.105
68.861 99.480 75.558
>> [vec,idx] = max(f,[],1); % value and row index of max in each column.
>> S = size(f); % size of input array.
>> idx = idx + S(1)*(0:S(2)-1); % convert row index into linear index.
>> out = C(idx) % use linear index to get elements of C.
out =
84.367 25.973 31.537
>> vec
vec =
4 33 333
その他の回答 (3 件)
madhan ravi
2019 年 2 月 8 日
C(any(f(:)==max(f),2)).'
13 件のコメント
Stephen23
2019 年 2 月 8 日
Note that this is very fragile code, and it can easily fail when values repeat in matrix f:
>> f = [1,22,333;4,33,111;1,4,33]
f =
1 22 333
4 33 111
1 4 33
>> C = [41.0875,66.4048,31.5374;84.3670,25.9733,73.1052;68.8608,99.4798,75.5581]
C =
41.087 66.405 31.537
84.367 25.973 73.105
68.861 99.480 75.558
>> C(any(f(:)==max(f),2)).'
ans =
84.367 25.973 99.480 31.537 75.558 % <- why five output values?
See my answer for code that actually delivers what the question asked for: " I want to select 3 elements from the matrix C, one element from each column..."
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