find a value and their related values in other columns

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SADRA SADEGHINEJAD 2020-4-6

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评论： SADRA SADEGHINEJAD 2020-4-6

Hi, i have a matrix included some rows and columns and I want to find some certain values in the first columns then make a new matrix with them. I have tried with different ways but i couln`t reach to the solution.

example : let`s we have a matrix like this

degree cl

-3 0.01

0 0.04

+3 0.06

6 0.08

9 0.09

now I wanna find where the degree is +3 and 6 and then find their related value of Cl for them

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Answer 1

KALYAN ACHARJYA 2020-4-6

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https://ww2.mathworks.cn/matlabcentral/answers/515842-find-a-value-and-their-related-values-in-other-columns#answer_424388

编辑：KALYAN ACHARJYA 2020-4-6

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Let's example

mat=[-3        0.01
0         0.04       
+3        0.06
6         0.08
9         0.09];
data_cl=mat(find(mat(:,1)==3 | mat(:,1)==6),2)

or you can use table for the same

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KALYAN ACHARJYA 2020-4-6

编辑：KALYAN ACHARJYA 2020-4-6

在 MATLAB Online 中打开

Sure, use the any required logical indexing, to met the required condition, as you mentioned in the question

find(mat(:,1)==3 | mat(:,1)==6)

Gives the row index of the particular values, then you can ge the cl of respectice data in 2nd column

SADRA SADEGHINEJAD 2020-4-6

i didn`t find solution for the following problem:

if we have large matrix and for instance we have angles like -3,0,3,6.... it is difficult and also not rational to do this way ( data_cl=mat(find(mat(:,1)==3 | mat(:,1)==6),2) )

how we can solve it? is it possible to find them by loop,if ....? actually i tried this but i have just get the last value of the loop

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