How to add a column to a matrix by matching element (attached data)

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Ismaeel
Ismaeel 2018-7-26
回答： Ismaeel 2018-7-26
Hi I have two matrices A and B with different sizes; B is smaller in size than A. I want to add another column to A by matching elements in both matrices. A small version of my data is as follows:
A=[
1 AUBURN 1 1.035108 1.035108 -64.410133
2 AUBURN 1 1.03706 1.03706 -65.261659
3 AUBURN 1 1.032929 1.032929 -66.801544
4 AUBURN 1 1.037436 1.037436 -65.328455
5 AUBURN 1 1.036071 1.036071 -64.403333
6 AUBURN 1 1.035108 1.035108 -64.410133
7 AUBURN 2 1.042328 1.042328 -64.042951
8 AUBURN 2 1.043484 1.043484 -64.622293
9 AUBURN 2 1.042239 1.042239 -64.048946
10 AUBURN 3 1.040954 1.040954 -64.565492
11 AUBURN 4 1.041164 1.041164 -64.526456
]
B=[
1 AUBURN 1 43.976116
2 AUBURN 2 44.100992
3 AUBURN 3 44.179913
4 AUBURN 4 44.143322
]
The second column in both matrices contain names that I want to be used for matching the elements in both matrices. I want the last column in B to be added to A with the corresponding matched elements. The results should be as C:
C=[
1 AUBURN 1 1.035108 1.035108 -64.410133 43.976116
2 AUBURN 1 1.03706 1.03706 -65.261659 43.976116
3 AUBURN 1 1.032929 1.032929 -66.801544 43.976116
4 AUBURN 1 1.037436 1.037436 -65.328455 43.976116
5 AUBURN 1 1.036071 1.036071 -64.403333 43.976116
6 AUBURN 1 1.035108 1.035108 -64.410133 43.976116
7 AUBURN 2 1.042328 1.042328 -64.042951 44.100992
8 AUBURN 2 1.043484 1.043484 -64.622293 44.100992
9 AUBURN 2 1.042239 1.042239 -64.048946 44.100992
10 AUBURN 3 1.040954 1.040954 -64.565492 44.179913
11 AUBURN 4 1.041164 1.041164 -64.526456 44.143322
]
Any idea?
Thanks

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采纳的回答

Jason Whitfield
Jason Whitfield 2018-7-26
As an alternative, you could use tables to accomplish this. It already looks like your data is formatted as a table. To do it, define A and B as tables with matching column names for the AUBURN data. Then, you can simply run "C = join(A, B);" Since the column names match, MATLAB will automatically match up the rows based on the value of the AUBURN data column.
  2 个评论
Ismaeel
Ismaeel 2018-7-26
Thanks JW. "define A and B as tables with matching column names for the AUBURN data." Could you please elaborate the statement a little bit in terms of matlab code?
Jason Whitfield
Jason Whitfield 2018-7-26
Take a look at the excel workbooks I've attached. Notice that the columns you want to match between the tables have the same name, "C1". (I have no idea what this data is, so I'm sure you could give it a better name.) Since they have the same name, MATLAB knows to use the data in these columns to match the rows of the two tables. Now, in MATLAB, you can run the following code to get the result you want.
A = readtable('A.xlsx');
B = readtable('B.xlsx');
C = join(A, B);

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更多回答（2 个）

Adam Danz
Adam Danz 2018-7-26
编辑：Adam Danz 2018-7-26
Assuming A and B are cell arrays, I loop through each row of B, find the corresponding rows in A, and insert the data from B.
% Add column to A
A(:,end+1) = {0};
% Loop through B and add to A as needed
for i = 1:size(B,1)
rowIdx = strcmp(A(:,2), B(i,2));
A(rowIdx,end) = B(i,3);
end
  3 个评论
显示 1更早的评论
Ismaeel
Ismaeel 2018-7-26
Thanks Adam. My data are stored in excel sheets (huge amount of data). As you know, matrices are only for numerical values but my matching elements are char.
Adam Danz
Adam Danz 2018-7-26
That's why I'm assuming your data are stored in a cell array (or table) once you import them to Matlab, not a matrix. This solution will work of that's the case. JW's solution may be more appropriate if your data are stored in a table.

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Ismaeel
Ismaeel 2018-7-26
Thank you Adam, thank you Jason. Both methods work. Jason's method is relatively easier since there is no for loop.

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