How to find the another values in array

Question

singh 2015-4-18

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编辑： Stephen23 2015-5-4

Suppose I have a array A=

 73.21  32.2
11.1  3.32
30.4  19.64
12.6  77.3
 30.7  6.2  
  21 .9  42.5

Now I have another array which contain some values B =

1 9 20 23

Now I input a single no through input command called N=20

I wish to find that N(20) in column first and return corresponding values column second and column third in array A

Like it return value 30.7 and 6.2

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pfb 2015-4-18

Thanks for choosing my answer.

Anyway the other two other answers are perhaps better, in that they do not use "find".

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Answer 1

pfb 2015-4-18

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You could use the command "find".

 % this finds the row (if any) at which N appears in the first column of A
 r = find(A(:,1)==N);
 % this returns the corresponding values in the 2nd and 3rd columns of A
 v = A(r,[2 3]);
 % note that this is a row vector if N appears only once in the first column of A
 % It is a matrix if N appears more than once
 % It is an empty vector if N never appears.

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Stephen23 2015-5-4

编辑：Stephen23 2015-5-4

find is slower and not at all required. Use Image Analyst's solution.

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Answer 2

Image Analyst 2015-4-18

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Just use logical indexing. You don't even need find().

A=[...
 1, 73.21,   32.2;
 6, 11.1, 3.32;
 9, 30.4, 19.64;
 17, 12.6, 77.3;
 20, 30.7, 6.2;
 23, 21.9, 42.5]
% B is unused - not sure why it was even mentioned
B =[1  9   20  23];  
N = 20;  % Gotten from using the input() function.
row = A(:,1)==N  % N must be an integer.
output = A(row, 2:3)