Extract the index and find the value in other array that have the same extracted index?

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Willim
Willim 2019-2-5
编辑： Stephen23 2019-2-6
I have many arrays but in my question I'll minimize it to be understood for you.
if I have
t1=[ 1.0000 1.1000 1.2000 1.3000 1.4000 1.5000]
the corresponsing x for t1 is
x1=[ 0.1690 0.6491 0.7317 0.6477 0.4509 0.5470]
I have other iteration with different length than t1,x1 as showing below:
t2=[
1.0000 1.0100 1.0200 1.0300 1.0400 1.0500 1.0600
1.0700 1.0800 1.0900 1.1000 1.1100 1.1200 1.1300
1.1400 1.1500 1.1600 1.1700 1.1800 1.1900 1.2000
1.2100 1.2200 1.2300 1.2400 1.2500 1.2600 1.2700
1.2800 1.2900 1.3000 1.3100 1.3200 1.3300 1.3400
1.3500 1.3600 1.3700 1.3800 1.3900 1.4000 1.4100
1.4200 1.4300 1.4400 1.4500 1.4600 1.4700 1.4800
1.4900 1.5000
]
the corresonsing x2 for t2 is
x2=[
0.4427 0.1067 0.9619 0.0046 0.7749 0.8173 0.8687 0.0844 0.3998 0.2599
0.8001 0.4314 0.9106 0.1818 0.2638 0.1455 0.1361 0.8693 0.5797 0.5499
0.1450 0.8530 0.6221 0.3510 0.5132 0.4018 0.0760 0.2399 0.1233 0.1839
0.2400 0.4173 0.0497 0.9027 0.9448 0.4909 0.4893 0.3377 0.9001 0.3692
0.1112 0.7803 0.3897 0.2417 0.4039 0.0965 0.1320 0.9421 0.9561 0.5752
0.0598
]
I need for loop that can extarct the index for t2 that has same value in t1, then after finding the index for same value in t2 with t1 , find the coressponding x2 for each t2 that have same value in t1.
the output will be new x which is extracted from x2 and have same length of x1
  2 个评论
Sargondjani
Sargondjani 2019-2-5
编辑：Sargondjani 2019-2-5
Have a look at 'find'. there are some examples that will help you further. You can for example get row and column index and use a for loop over t1, with
[row,col]= find(t2 == t1(it1))
, something like that.

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采纳的回答

Bob Thompson
Bob Thompson 2019-2-5
You shouldn't actually need a for loop to do this, just some logic indexing.
goal = x2(ismember(t2,t1));
  1 个评论
Stephen23
Stephen23 2019-2-6
编辑：Stephen23 2019-2-6
Keep in mind that floating point error means that checking for exact equivalence of decimal values is not recommended, and can easily lead to unexpected outputs. For the data shown in the question it would be much more robust to use ismembertol.

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