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Working with tables: populate column of NaNs in table 1, with contents of column of table 2, given a condition.

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Ajpaezm
Ajpaezm on 19 Feb 2020
Answered: Jacob Wood on 19 Feb 2020
I have some data in testing.mat (uploaded to this thread), two tables with two common columns: 'letter' and 'vals'.
On t_1, my 'vals' column is full of NaNs, I'd like to fill it with the values of the 'vals' column of t_2. I managed to achieve this with a for loop and using strcmp.
My question for the forum is, is it possible to do this in a single line or two? Without "for" loops? I have not tried it yet, but outerjoin could help me, the thing is I think the command will leave the two 'vals' column if I do the merge using that key.
What do you recommend?

Accepted Answer

Jacob Wood
Jacob Wood on 19 Feb 2020
It is possible to do with a small amount of code. The easiest way to utilize a table like your "t_2", where the "letter" column contains unique values, is to label the rows. After labelling the rows you can use logical indexing to access the values you are looking to replace:
t_2.Properties.RowNames = t_2.letter; %Label rows
nan_idx = isnan(t_1.vals); %Find letters that need to be looked up
t_1.vals(nan_idx) = t_2(t_1.letter(nan_idx),:).vals; %Label these with values from t_2

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