Find adjacent values of a vector corresponding to another vector

Question

anton fernando 2017-12-21

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https://ww2.mathworks.cn/matlabcentral/answers/374142-find-adjacent-values-of-a-vector-corresponding-to-another-vector

回答： Jos (10584) 2017-12-22

Hi, I am trying to find the adjacent points of a 1-D vector corresponding to the elements of another column vector. It is very hard to explain. I will explain it from an example.

A=[ 11; 22; 32; 44; 51;]; B=[11.4 32.4 36.6]; So I need a matrix with the adjacent points of each element of the vector B of vector A as in, Ans1=[11 22; 32 44; 32 44;] also the corresponding locations as in, ans2[1 2; 3 4; 3 4;] Appreciate any help.

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Answer 1

Matt J 2017-12-21

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https://ww2.mathworks.cn/matlabcentral/answers/374142-find-adjacent-values-of-a-vector-corresponding-to-another-vector#answer_297389

在 MATLAB Online 中打开

idx=discretize(B,A); 
Ans2=[idx(:),idx(:)+1]; 
Ans1=A(Ans2);

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anton fernando 2017-12-22

在 MATLAB Online 中打开

Your answer worked for my example. But it doesn't work for my data set. Let me get you my data set.

A=[1
1
71100003
62000000
53899997
46700001
40200001
34500000
29499999
25299999
21699999
18600000
16000000
13699999
11700000
099799998
085000001
072499998
061799999
052600000
044700000
037999999
032299999
027400000
023200000
019700000
016700000
014100000
011900000
0099799996
0083999997
0070600002
0059400001
0049999999
0042099999
0035500000
0029899999
0025200001
0021200001
0018000000
0015200000
0012900000
0011000000
00094200001
00080699997
00069299998
00059700001
00051400001
00044300000
00038200000
00033000001
00028599999
00024800000
00021499999
00018800001
00016400000
00014300000
00012600000
00011000000
6999996e-05];
B=[0.986923267000000
672382994000000
458089201000000
312092540000000
212626172000000
144860520000000
0986923270000000
0672382990000000
0458089200000000
0312092540000000
0212626170000000
0144860520000000
00986923300000000
00672383000000000
00458089200000000
00312092500000000
00212626200000000
00144860520000000
000986923000000000
000672383000000000
000458089000000000
000312093000000000
000212626000000000
000144860000000000
86923000000000e-05];

Thank you in advance.

anton fernando 2017-12-22

编辑：anton fernando 2017-12-22

I am sorry. I meant by not sorted that there can be NaN values and repeated values in the vector. But initially I don't have to worry about it. But sure, I can flip the matrix and make it monotonically increasing. But vector A is monotonically decreasing.

anton fernando 2017-12-22

Once you flipped the matrices it works. Thanks. :)

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Answer 2

Jos (10584) 2017-12-22

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https://ww2.mathworks.cn/matlabcentral/answers/374142-find-adjacent-values-of-a-vector-corresponding-to-another-vector#answer_297432

在 MATLAB Online 中打开

Here is a solution that finds the element in A that is just before or just after each element in B.

A=[ 11; 22; 32; 44; 51;]; B=[11.4 32.4 36.6]
clear ans2
ans2(:,1) = nearestpoint(B, A, 'before') ;
ans2(:,2) = nearestpoint(B, A, 'after') ;
ans1 = A(ans2) % will fail when elements of B do not fall between elements of A. Check for that!

My NEARESTPOINT utility can be downloaded from the File Exchange:

https://uk.mathworks.com/matlabcentral/fileexchange/8939-nearestpoint-x--y--m-