How to get values ​​from a column based on the values ​​of other columns?

Hi,

I ordered a set of data as in the example below:

   A   B  C   D  E  F  G    J
,1985,04,10,1800,4,140,1,  2.0,
,1985,04,11,0900,4,999,1,  0.0,
,1985,07,09,0300,4,999,1,  0.0,
,1985,04,11,2100,4,020,1,  5.0,
,1987,03,03,1000,4,360,1, 10.0,
,1987,03,03,1100,4,360,1, 10.0,
,1987,01,03,0700,4,360,1,  8.0,
,1987,01,03,0900,4,360,1,  7.0,
,1987,03,03,1200,4,360,1, 10.0,
,1987,03,03,1300,4,360,1, 10.0,
,1985,07,09,1500,4,180,1, 10.0,
,1985,07,09,1800,4,180,1, 11.0,
,1985,07,10,0600,4,160,1,  3.0,
,1985,07,10,1000,4,180,1,  4.0,
,1985,04,11,1500,4,360,1,  9.0,
,1985,04,11,2000,4,050,1,  5.0,
,1985,07,10,1200,4,180,1,  5.0,
,1985,07,10,1500,4,180,1,  6.0,
,1987,01,03,0600,4,360,1,  8.0,
,1987,01,03,1100,4,360,1,  6.0,
,1985,07,09,0600,4,999,1,  0.0,
,1985,07,09,1200,4,180,1,  6.0,
,1987,01,03,1300,4,360,1,  6.0,
,1987,01,03,1600,4,360,1,  7.0,
,1987,01,03,1900,4,360,1,  6.0,
,1987,03,03,0500,4,020,1,  8.0,
,1987,03,03,0900,4,360,1, 10.0,
,1987,01,03,1400,4,320,1,  5.0,
,1987,03,03,1500,4,360,1, 10.0,

I want to create an array with the values in column "J" based on the values in column "B". . For example the vector Z should contain only the values of "J" that are on the same row with the value "01" in column "B", vector X only the "03" and so on ...

Thanks in advanace for the help and suggestions.

Answer 1

[Michael Haderlein]

Are A...J cell arrays with strings or numeric arrays?

If you have numbers, this should do the job:

Z=J(B==1);

If it's cell arrays with strings, you need:

Z=J(strcmp(B,'01'));

Best regards,

Michael

[Nym]

Thank You, I tried but I dont get the correct values... I'l try some more

[Nym]

In the end the problem was with the dataset now I have the correct answer. Thanks for the help.

As a side note I tried the other answers once I realized the error and are right now... Thank you all

Answer 2

[Joseph Cheng]

you can use == to find the rows for each B value. here is an example of an implementation

uB = unique(MatAnsExample(:,2));

for ind = 1:length(uB)
    Result(ind).B = uB(ind);
    Result(ind).J = MatAnsExample(MatAnsExample(:,2)==uB(ind),8);
end

here i find each unique instance of values within column B. then with the for loop i store the current B in the Result structure as well as the values of J that correspond with that B. to do this i generate the logical mask of when column B is equal to the B in question.

[Nym]

Seems that i failed to make myself understood, sorry. I need a new vector with J values only that are on the same row with a specific value from B, not entire row. In the example above:

Z = [8.0 7.0 8.0 6.0 6.0 7.0 6.0 5.0]

Thank you for support.

[Guillaume]

Joseph's answer is correct and creates all the possible vectors out of your matrix. If you just want one vector, you can simplify it to:

Z = m(m(:, 2) == 1), 8);

[Nym]

Thank you but I fail to adapt to my needs suggested code, my knowledge of MATLAB is poor.

[Joseph Cheng]

so if you run my code lets say with an adaptation

uB = unique(MatAnsExample(:,2));
for ind = 1:length(uB)
    Result(ind).B = uB(ind);
    Result(ind).J = MatAnsExample(MatAnsExample(:,2)==uB(ind),8);
    disp(['For a B of: ' num2str(uB(ind)) ' the J column are: ' num2str(Result(ind).J')]);
end

you get the results

For a B of: 1 the J column are: 8  7  8  6  6  7  6  5
For a B of: 3 the J column are: 10  10  10  10   8  10  10
For a B of: 4 the J column are: 2  0  5  9  5
For a B of: 7 the J column are: 0  10  11   3   4   5   6   0   6

you get the examples you just wrote. so instead of using individual variables Z, X, Y, etc. for each value of B. I am storing it as Result(N) where N from 1 to the number of unique instances within the B column. So to get the Z, X, etc. variable you can simply just type in Result(1).J instead. I also just put it in this form as i don't know what you are doing. The Right side of the equation is what you should be interested in and not the left side. The left side is for you to determine.