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# Graphs not working with previously defined symbols

## Graphs not working with previously defined symbols

(OP)
Specific problem:
I have a function w(s) = ...
When I try to graph the function using the variable 's', I get an error because the graph thinks s is a second and not a variable.
s:=s doesn't work as implied on other web pages.
How do I undefine s?

General problem:
The above doesn't seem to work for any previously defined symbol (x, t, L, etc).
Is it possible to graph using a previously defined symbol as it's variable?

Thanks!

http://www.imakenews.com/ptcexpress/e_article001226767.cfm?x=bdw558S,bb9TNsfb

### RE: Graphs not working with previously defined symbols

That's the whole point, isn't it?  A variable is an unknown.  If you don't define it ahead of time, Mathcad will generate a single variable plot using the range of -5 to 5.

However, if a variable is already defined, then you need to make it into a range variable or vector to get a plot.

If you are otherwise not using units, you could turn off the units altogether.

### RE: Graphs not working with previously defined symbols

(OP)
Thanks for steering me toward ranges.  I made s an array:
i:=0..100
s[i:= -50ft + i*2ft

w(s) now graphs, yay!

Although the above takes a some thought to set up right.  I'm wondering if there is an easier way?  It would be ideal if there were a way to undefine a unit.

I do need units, I don't want to disable them completely.

### RE: Graphs not working with previously defined symbols

In my case, I do use units, and I just avoid reusing built-in units, because the consequence of redefining a common unit can be quite annoying.

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