Question

matlab中 S函数 显示没有定义变量t是怎么回事

Answer 1

你在用t作为变量时没有申明。可以这样定义变量x：
>> syms x;
>> y=x^2+1;
>>
定义完毕之后就不再显示没有定义变量

Answer 2

>> help varargin
VARARGIN Variable length input argument list.
Allows any number of arguments to a function. The variable
VARARGIN is a cell array containing the optional arguments to the
function. VARARGIN must be declared as the last input argument
and collects all the inputs from that point onwards. In the
declaration, VARARGIN must be lowercase (i.e., varargin).

For example, the function,

function myplot(x,varargin)
plot(x,varargin)

collects all the inputs starting with the second input into the
variable "varargin". MYPLOT uses the comma-separated list syntax
varargin to pass the optional parameters to plot. The call,

myplot(sin(0:.1:1),'color',[.5 .7 .3],'linestyle',':')

results in varargin being a 1-by-4 cell array containing the
values 'color', [.5 .7 .3], 'linestyle', and ':'.

See also varargout, nargin, nargout, inputname, function, lists, paren.

Reference page in Help browser
doc varargin