Info

此问题已关闭。 请重新打开它进行编辑或回答。

How to use a math function as an input in a written function?

3 次查看（过去 30 天）
andrew
andrew 2014-9-23
关闭： MATLAB Answer Bot 2021-8-20
I have written a function and am trying to call it using x*sin(x) as an input variable. Of course x must be defined so I use @(x) x*sin(x) but this triggers an error Unexpected matlab operator. How do I use this as an input variable correctly?
important things:
function[x,u]=finite_difference_laplace(func,a,b,N,u_a,u_b)
h=(b-a)/(N-1);
x=a:h:b;
A=zeros(N-2,N-2);
A(1,1)=-2;A(1,2)=1;A(N-2,N-2)=-2;A(N-2,N-3)=1;
for i=2:1:N-3
A(i,i-1)=1;
A(i,i+1)=1;
A(i,i)=-2;
end
b=h.^2*[func(x(2))-u_a,func(x(3:N-2)),func(x(N-1))-u_b];
uu=A\b;
u=[u_a;uu;u_b];
>> finite_difference_laplace(@(x) x*sin(x),0,10,7,0,1)
|
Error: Unexpected MATLAB operator.
  5 个评论
显示 3更早的评论
andrew
andrew 2014-9-23
I'm not actually sure. Usually, when I try to run a file a window pops up and I click Add to path and that's that. How can I check that it's on path?
Adam
Adam 2014-9-23
which finite_difference_laplace
will tell you if it is on your path (if it isn't it will say not found), but I think you would get a different error message anyway if the function is not on your path.
If you go to 'Set Path' (I can't remember where it is in R2012a - does that version have the ribbon stuff at the top?) you can see your full path and click 'Save' to ensure that something you add to your path in one session remains on your path in the next session. I would advise using the 'Move to Bottom' option on your added folders, but that is just my preference as I have had some odd conflicts caused by having my own folders above the Matlab main folders in the past.

此问题已关闭。

回答（2 个）

Titus Edelhofer
Titus Edelhofer 2014-9-23
Just to be sure: your MATLAB version is not R12 or R13 from before 2003? In R14 anonymous functions were introduced ...
Titus
  4 个评论
显示 2更早的评论
John D'Errico
John D'Errico 2014-9-23
编辑：John D'Errico 2014-9-23
2012a is recent enough to have function handles like this, but the unexpected operator message indicates an older release to be the most likely cause.
Iain
Iain 2014-9-23
I would have said that the error message was most likely to indicate user error (most likely to be a typo.)
andrew
andrew 2014-9-23
Ok guys, I'm not sure what happened but it is working now. I went to my prof. and he defined func=@(x) x*sin(x), then used func as an input. But I said that seemed like an alternative (not a solution), and he said you could also just use @(x) x*sin(x), and he typed it in and it worked (aside from the dimensional errors in h that I fixed later). But I swear that was what I was doing beforehand. I used clear and ran it again just in case and it still worked.
>> finite_difference_laplace(@(x) x*sin(x),0,10,7,0,1)
ans =
0 1.6667 3.3333 5.0000 6.6667 8.3333 10.0000

此问题已关闭。

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by