Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations waross on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Reset variables in MathCAD

Status
Not open for further replies.

jtdoug

Aerospace
Dec 25, 2007
2
US
If a variable has been defined numerically. How can it be released for subsequent reuse symbolically?

Of coarse the variable can be reassigned, but how can it be deassigned?

 
Replies continue below

Recommended for you

Sometimes, that works, sometimes, it doesn't.

However, I'm not fully convinced there's a real need to "reuse" a variable name. If it's going into the same calculation, then some sort of indexed variable should be used. If it's going into another equation, then a new name should be picked. Even if you can deassign a variable, the usage of the same name implies that the variable is being reused, as is, since the reader might not even notice the deassignment.

TTFN

FAQ731-376
 
Some times you want to 'de-assign' a variable so that the symbolic processor will use the variable name, rather than its defined value.
[actually what is happening is that it becomes a self recursive definition]
e.g. if r:=5 and then we define area:=pi*r^2 we can ask the value of area=xx.x but we can't easily ask for the symbolic differential because mathcad will think that all the values are fixed so the differential is zero.

If we insert an r:=r then the symbolic engine will know to stop at the recursion and give d/dr(area) -> 2*pi*r

Further, you can pre assign the result to a function
circ(r):= d/dr(area) -> 2*pi*r

If later you update the formula for area, the follow on equations will live update as well, and you will be able to use the default numeric value that was already in place for r [i.e. the r=5 above].

It just takes a little care to make it look neat sometimes. e.g. place the r:=r just across the right margin for a pretty print

Philip
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor

Top