How do I add a column to a cell array based on existing values in another column?

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nskel 2019-6-6

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评论： nskel 2019-6-6

Hi,

Only a beginner so forgive me for the basic question... but I have a cell array (x) of dimensions 1310x2. Column 1 is a unique identifier; there are two possible values of the second column, either "A" or "B". I want to add a third column which I want to be "1" if Column 2 is "A" and "0" otherwise.

What is the most efficient way to carry this out?

Should I be using an 'if' statement with a loop?

If so, should I be adding a third (blank) column before carrying out the if statement and populating this with 1's or 0's?

Thanks!

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nskel 2019-6-6

Thanks for the answers guys! Really appreciate it... Just out of curiosity let's say instead of 'A' and 'B' Column 2 was made of 2 numerics, say 100 or 200- what is the equivalent to strcmp for numbers in this context or is there a better way to go about it?

Cheers!

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Answer 1

Alex Mcaulley 2019-6-6

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One option is:

x(:,3) = deal({0});
x(ismember(x(:,2),'A'),3) = deal({1});

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Jan 2019-6-6

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Cheaper without deal():

x(:,3) = {0};
x(strcmp(x(:,2),'A'), 3) = {1};

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Answer 2

Jan 2019-6-6

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编辑：Jan 2019-6-6

在 MATLAB Online 中打开

Only a beginner so forgive me for the basic question... but I have a cell array (x) of dimensions 1310x2. Column 1 is a unique identifier; there are two possible values of the second column, either "A" or "B". I want to add a third column which I want to be "1" if Column 2 is "A" and "0" otherwise.

x = {'id1', 'A'; ...   % Test data
     'id2', 'B'; ...
     'id3', 'A'};
Value  = {'1', '0'};   % Or do you mean {"1", "0"}, or {1, 0}?
x(:,3) = Value(2 - strcmp(x(:,2), 'A'));