Code to zero the elements above major diagonal

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Tiny Rick
Tiny Rick 2018-10-21
评论： James Tursa 2018-10-22
Hi, I’m finding an inverse of a matrix using Gaussian elimination. So, the first step is that I had to carry out row operations zero the elements below the diagonal and that has no problem with me. The problem is I don’t know what code I need to write on the script to zero the elements above the major diagonal. If I could get an answer for that it would be very great. Thank you.
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James Tursa
James Tursa 2018-10-22
Please post your code and then tell us what steps you are doing or output you are getting that you think needs fixing.

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回答（2 个）

madhan ravi
madhan ravi 2018-10-22
Example:
A = ones(4)
B = tril(A)
Or
B= tril(A,1)
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Tiny Rick
Tiny Rick 2018-10-22
Do you have a specific formula to be written as a code to carry out the row operations?
madhan ravi
madhan ravi 2018-10-22
you mean rref? example of your output is there in my answer?

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Tiny Rick
Tiny Rick 2018-10-22
What I mean is there are values for the elements above the diagonal let’s say a matrix;
[5 7 9;0 4 2;0 0 3]
Do you have a formula that can be to carry out the row operations so that we can reduce the elements above the diagonal to zero? And It can accept any size of matrix
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Steven Lord
Steven Lord 2018-10-22
Since this is almost certainly a homework assignment, your textbook probably has some pseudocode you can adapt into a function.
If this is not a homework assignment, don't invert and/or use Gaussian elimination. Use the backslash operator \ to solve your linear system of equations, or (if you absolutely must compute the inverse) use the inv function.

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