Undefined function error. How to correct ?

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 ??

Answer 1

[Walter Roberson]

Start with

syms r

As expand() is part of the symbolic toolkit.

[Matt Fig]

Now that would clear things up a bit!

[Pankaj Wagh]

I am facing the same Undefined Error for the raylrnd function. Can you suggest any solution for that?

Answer 2

[Matt Fig]

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.

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.

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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?

[Bhagat]

Yes, I don't see it.

I want to expand(1-x)^6. How do I do it ?

[Bhagat]

Sorry my mistake. It is x=(1-r).^2 in the error.

How do I define r ?

Yes , I tried the help example.---

expand((i-2)*(i-4))---

in the command window.It gave the following error----

??? Undefined function or method 'expand' for input arguments of type 'double'.

-----------

[Bhagat]

I am very new to MATLAB. These might be very basic doubts, but I've just started.Will appreciate help.

[Matt Fig]

You need to make sure the EXPAND function is in the current directory or on your search path.

[Bhagat]

x is a vector. The function (1-x) has to be expanded to the power of 6. As (1-x)^2 expands to x^2-2*x+1.

[Matt Fig]

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]

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