General questions about function and if command.

1 次查看（过去 30 天）
C Zeng
C Zeng 2012-10-23
1. If I have a variable x, and I use a nested function f and in f.m, there is also a variable x but not equal to the first x. Will it bother the program? The x's are defined in different functions, will matlab recognize these?
2. I have an error message: --- Operands to the and && operators must be convertible to logical scalar values.
Error in V_F (line 16) if P(n)>0 && x>n-1 ---
However, P(n) is scalar and x is also scalar. What is wrong here?
Thanks.

请先登录，再回答此问题。

回答（2 个）

Matt Fig
Matt Fig 2012-10-23
编辑：Matt Fig 2012-10-23
For the first question, it makes a difference how and where you are accessing the variables. Post a simple example for anlaysis. For the second question, are you sure P is not a cell array and P(n) is not nan? Are you sure n is a scalar and not empty or nan? Are you sure x is a scalar and not empty or nan?
  1 个评论
C Zeng
C Zeng 2012-10-23
Hi, Matt, thanks in advance!
(1) For example, in my current program, I define x as a vector, like x=zeros(1,N). I also define a function f(a,b,c) note f has nothing with x. In f.m file, I write a code to find the f_value, including define auxiliary variable x which is a scalar. By doing so, it seems to me that it will not affect any confusion, and by convention, matlab will not make any problem, right?
(2)Let me double check it. I think they are all well defined and will not be empty or infinity.

请先登录，再进行评论。

Walter Roberson
Walter Roberson 2012-10-23
There might perhaps be a code path in which your local "x" does not get initialized in the subfunction on and so inherits the scalar value.
  3 个评论
显示 1更早的评论
Walter Roberson
Walter Roberson 2012-10-23
Suppose you have
if a > 3
x = 15;
elseif a < 3
x = 22;
end
then it might at first look like x is always being initialized, but in fact in the case that a is exactly 3, there would be a path in which x was not set, and so in that case would inherit its value from the nesting function.
C Zeng
C Zeng 2012-10-26
Thanks, Walter, so in this case x is not well defined? Will it cause any problem to nested function?

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Data Type Conversion 的更多信息

标签

Community Treasure Hunt

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

Start Hunting!

Translated by