I have a matrix with 3 columns. How can I find the differences between column 2 and 3 for each value on column 1 and add the results as a 4th column into the same matrix?

I have a matrix with 3 columns. How can I find the differences between column 2 and 3 for each value on column 1 and add the results as a 4th column into the same matrix?

[Image Analyst]

I have a question about what exactly "for each value on column 1" means. What if this is your matrix

1 2 3
2 6 9
1 5 10

Column 1 has two values 1 and 2. What do you want column 4 to be? The "1" value will have two differences, not just one difference? So do you want the average of the two differences? Or do you want the difference per row rather than "for each value in column 1"?

[Efe IST]

"Warning: Out of range or non-integer values truncated during conversion to character."This came out when I used this code." MATLAB popped this up after I used it.

and sorry for the unclarity. Yes, I do want the difference per row and put it as a fourth row on the same matrix.

[Walter Roberson]

What is the data type of your array? It sounds like it might be char() . If it is, then how do you define the "difference" between two characters?

[Image Analyst]

What code did you use? Show your code, including the code that generated the initial matrix.

Answer 1

[Image Analyst]

Not sure what you're asking but I'm taking a guess that you want the differences on a row-by-row basis rather than what you said. So would this work?

m = [m, m(:,3)-m(:,2)]; % Append (col3-col2) onto original m