Comparing two tables and copy elements of table 2 into table 1

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Haritha
Haritha 2019 年 3 月 14 日
コメント済み: Ayse YILMAZ 2021 年 4 月 19 日
Hi,I have two tables as given below.
Table 1:
Table 2
If column1 in table 2 is equal to column 1 in table1 T & W values in table 2 has to copy in table 1, Similar strings has to follow one after the other. If the stings are unequal T & W must be empty. I want the output as below table;
image.PNG
  2 件のコメント
dpb
dpb 2019 年 3 月 14 日
Your new table now has three 'hi' records instead of original two but only two 'hello'.
What's the difference and what's the logic behind such that could be written?
Haritha
Haritha 2019 年 3 月 15 日
Hi,
I will edit that table

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採用された回答

Guillaume
Guillaume 2019 年 3 月 14 日
%create demo tables
ID = strsplit('hello new world hi hello hi')';
T = cell(6, 1); W = T;
V = [1; 2; 3; 5; 8; 7];
T1 = table(ID, T, W, V)
T2 = table(ID(4:5), {2;4}, {6;7}, [1;2], 'VariableNames', {'ID', 'T', 'W', 'V'})
%merge the two tables
[found, where] = ismember(T1.ID, T2.ID);
T1(found, {'T', 'W'}) = T2(where(found), {'T', 'W'})
  3 件のコメント
Haritha
Haritha 2019 年 3 月 20 日
Its working for normal tables. I forget to mention the SQL. I accepted my mistake
Ayse YILMAZ
Ayse YILMAZ 2021 年 4 月 19 日
Hello Guillaume;
Firstly thank you for your helpful sharing. I have a question about your answer.
When I run your code in Matlab, it returns 0 as the value that is not in T2. I wonder if there is a way to return it as space or NAN or something else? What code should I write for this?
Another question is what should I do for more than two tables comparison (7 or 8 tables)?
Thank you in advance for your answer.

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その他の回答 (2 件)

Pruthvi G
Pruthvi G 2019 年 3 月 14 日
Use
strcmp
if the values are matching then add the values to the T and W column
  1 件のコメント
Guillaume
Guillaume 2019 年 3 月 14 日
ismember which uses strcmp would be a lot more useful for this.

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Peter Perkins
Peter Perkins 2019 年 3 月 20 日
This is just an outer join:
>> T1 = table(["hello";"new";"world";"hi";"hello";"hi"],[1;2;3;5;8;7],'VariableNames',["Word" "V"])
T1 =
6×2 table
Word V
_______ _
"hello" 1
"new" 2
"world" 3
"hi" 5
"hello" 8
"hi" 7
>> T2 = table(["hi";"hello"],[2;4],[6;7],'VariableNames',["Word" "T" "W"])
T2 =
2×3 table
Word T W
_______ _ _
"hi" 2 6
"hello" 4 7
>> outerjoin(T1,T2,'MergeKeys',true)
ans =
6×4 table
Word V T W
_______ _ ___ ___
"hello" 1 4 7
"hello" 8 4 7
"hi" 5 2 6
"hi" 7 2 6
"new" 2 NaN NaN
"world" 3 NaN NaN
  1 件のコメント
Guillaume
Guillaume 2019 年 3 月 20 日
編集済み: Guillaume 2019 年 3 月 20 日
Do'h! I did try using an outerjoin but using only Word as the key hence got duplicate V, T and W in the result, which I couldn't merge. Of course, If you use all columns as keys, then you get the correct outerjoin.
Note that since the data is stored in a database you don't need matlab to do the join. In SQL it'd be something like:
SELECT * FROM table1 FULL OUTERJOIN table2 ON table.Word = table2.Word

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