Evaluate matrix equation at multiple timesteps
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How can I evaluate a matrix equation at multiple timesteps? I've defined the following:
R=[1 0.5; 0.5 1];
M0=[1;1];
u0=[1;0];
x=linspace(0,1,100)
f=@(x) expm(-R.*x)*(u0-M0) + M0;
y=feval(f,x);
However, this gives an error as x is the 'wrong size' for matrix multiplication. However, I don't want to do matrix multiplication, but instead evaluate f at every value of x.
2 个评论
Even if x is a scalar, your code produces multiple y values:
>> x = 1;
>> expm(-R.*x)*(u0-M0)
ans =
0.19170
-0.41483
Is this correct? Or do you expect one y value for each x value?
Mark
2019-1-11
采纳的回答
Stephan
2019-1-11
1 个投票
Hi,
try:
R=[1 0.5; 0.5 1];
M0=[1;1];
u0=[1;0];
x=repmat(linspace(0,1,100),2,1);
y = zeros(2,size(x,2));
f=@(x) expm(-R.*x)*(u0-M0) + M0;
for k = 1:size(x,2)
y(:,k)=f(x(:,k));
end
plot(x(1,:),y(1,:),x(1,:),y(2,:))
result it:
Due to the matrix multiplication, i used a for loop. I think bsxfun should also be possible to do this.
Best regards
Stephan
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