Compare values from two text files and replace if they match

I have a problem of comparing two text files and replace value in third column if values in two first column match.

I have to text files. Each with tree columns (with the same format).

Text file 1 (short example):

177.50 0.00 1

180.00 0.00 1

0.00 10.00 1

2.50 10.00 1

5.00 10.00 1

7.50 10.00 1

10.00 10.00 1

12.50 10.00 1

Txt file 2 (short example):

2.50 10.00 0.01177

2.50 20.00 0.00977

5.00 0.00 -0.01480

5.00 10.00 -0.01244

5.00 20.00 -0.00440

5.00 30.00 -0.00228

I want to compare values of the first and second column in Text file 1 with the values in first and second column in Text file 2. If both values matches I want to replace “1” in third column in Text file 1 by corresponding value from third column from Txt file 2. The final output will be modified Text file 1 where in third column will be “1” in rows “not present” in Txt file 2 and values from Txt file 2 – in rows which match to Txt file 2.

For presented example output Text file 1 should look like this:

177.50 0.00 1

180.00 0.00 1

0.00 10.00 1

2.50 10.00 0.01177 %“1” was replaced by 0.01177 because this value is in Text file 2 in row “2.50 10.00”

5.00 10.00 -0.01244 %“1” was replaced by -0.01244 because this value is in Text file 2 in row “5.00 10.00”

7.50 10.00 1

10.00 10.00 1

12.50 10.00 1

Would be great if someone could help me out! Thanks in advance!

[Bob Thompson]

What does your script look like so far?

Answer 1

[Guillaume]

Assuming you've imported your two text files as matrices:

%m1, m2: matrices corresponding to each text file:
[ismatch, whichrow] = ismember(m1(:, [1 2]), m2(:, [1 2]), 'rows');  %find which rows match and where the match is in m3
m1(ismatch, 3) = m2(whichrow(ismatch), 3);   %replace column 3 of m1 by column 3 of m2 for match

Note that if there are duplicate matches in m2, the first one will be used.

[UWM]

Thank you very much :)