Solving Matrices with Symbolic Variables

2011 11 30
3 个回答
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更新时间：2023 11 13
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1 个投票

I am trying to figure out how to solve a problem such as [A]{X}={0} where [A] is a numerical matrix such as
[1 2 3 4]
[5 6 7 8]
[9 0 1 2]
and {X} is a symbolic matrix with a single numeric value such as
[1x1 sym; 1x1 sym; 1x1 sym; 1]
that is:
[a]
[b]
[c]
[1]
Is there a way to find a,b,c such that [A]{X}={0}

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Walter Roberson
Walter Roberson 2020-6-2
null() by itself does not work for the case where one or more of the X vectors are known constants, as is required by the Question.

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 采纳的回答

Andrei Bobrov
Andrei Bobrov 2011-11-30

0 个投票

A =[ 1 2 3 4
5 6 7 8
9 0 1 2]
syms a b c
x = [a;b;c]
k = A(:,1:3)\-A(:,end);
for i1 = 1 : numel(x)
eval([char(x(i1)),'=k(i1)']);
end

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Jared
Jared 2011-11-30
thanks alot works well, one minor adjustment:
k = cell2mat(A(:,1:3))\-cell2mat(A(:,end));
Karan Gill
Karan Gill 2016-12-1
It's much simpler. See Kaixiang Wang's answer below.
JITHA K R
JITHA K R 2018-1-4
Can you explain the working of this code pls?

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更多回答（2 个）

Kaixiang Wang
Kaixiang Wang 2016-11-30
编辑：Kaixiang Wang 2016-11-30

3 个投票

Simply use MATLAB symbolic toolbox and the solve() function.
syms a b c
A=[1 2 3 4;5 6 7 8;9 0 1 2]
X=[a;b;c;1]
sol=solve(A*X)

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Shivam Prajapati
Shivam Prajapati 2020-6-2
Null(A) % null is matlab command
Walter Roberson
Walter Roberson 2020-6-2
null() by itself does not work for the case where one or more of the X vectors are known constants, as is required by the Question.

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