Undefined function error. How to correct ?

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Bhagat
Bhagat 2011-3-2
评论： Pankaj Wagh 2021-4-13
I am trying to use the expand function. As a simple example i am trying to execute the following code as an m-file.
x=(1-r).^2; y=expand(x);
But it gives the following error: -------- ?? Undefined function or variable 'r'.
Error in ==> test at 1 l=(1-r).^2; ----x----
How to correct this error ??

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采纳的回答

Walter Roberson
Walter Roberson 2011-3-2
Start with
syms r
As expand() is part of the symbolic toolkit.
  2 个评论
Matt Fig
Matt Fig 2011-3-2
Now that would clear things up a bit!
Pankaj Wagh
Pankaj Wagh 2021-4-13
I am facing the same Undefined Error for the raylrnd function. Can you suggest any solution for that?

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更多回答（1 个）

Matt Fig
Matt Fig 2011-3-2
It would seem you need to define r. Try putting a WHOS right before the line that errors (or put a break point above that line and query the same way):
whos
x=(1-r).^2;
y=expand(x);
If you don't see an r in the list, you don't have r defined in the scope of the code. This is not a problem of the EXPAND function, but of your not having defined r where the code you are trying to execute can see it.
.
.
.
And why does the error indicate the problem is a line that looks like this:
l=(1-r).^2
but you showed the code as:
x=(1-r).^2
And did you read the help for EXPAND? Does it work with only one input according to the help?
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Matt Fig
Matt Fig 2011-3-2
Look at Walter's suggestion:
syms x
expand((1-x)^2)
I bet there is help for the EXPAND function available by typing:
help expand
Bhagat
Bhagat 2011-3-2
Yes, i got that.
I had searched expand for help. But it wasn't mentioned that it is a part of symbol toolkit. Thanx anyway

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