"IF" function with undefined "OTHERWISE" item?

Question

"IF" function with undefined "OTHERWISE" item?

Briscoz (Computer)

(OP)

26 Mar 08 06:07

Hi,
Please, could you help me? I have problem with "IF" function. I have function named "f1" and "f2".
f1:=0..10
f2:=0..10
Sum of these function cannot be greater that 10. If the sum is greater, then function is undefined.

I tried do that by the help of the "IF" function.
if(f1+f2<10,f1+f2,0)
But there is "OTHERWISE" item. I use "0", but would like to use "UNDEFINED", or something like that.

It is possible to do that?

Thanks

IRstuff (Aerospace) · Answer 1 · 2008-03-26 10:10:30

You can specific a text output using UNDEFINED in quotes.

TTFN

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jghrist (Electrical) · Answer 2 · 2008-03-26 12:33:17

But the funcion won't work because you can't compare the results of adding two range variables to a scalar. Try creating a vector and comparing each element.

pstuckey (Electrical) · Answer 3 · 2008-03-26 18:29:06

What you may be looking for is NaN (no quotes), which will define a result as Not a Number.

Peter

philipoakley (Aerospace) · Answer 4 · 2008-03-27 05:33:31

Bizcoz,
Unfortunately you don't have what you think you have.
As written, what you have is two range variables - these are implied for loops.

You can assign NaN (Not a Number) to a result to indicate undefined.

I presume you are doing 'numeric' calculations rather than fancy formula manipulation (symbols).

f1(a):=a
f2(b):=b
[f1, f2 not really needed]

F3(a,b):=if(a+b>10,NaN,a+b)

Philip
Stick a work sheet on http://collab.mathsoft.com/~Mathcad2000 for more replies

Briscoz (Computer) · Answer 5 · 2008-03-31 06:19:15

Thanks,
It is fact, that I didnt need funcitons f1 and f2 :) ,
but NaN didn´t help me :(

When I used NaN, then 3d graph diseppeared. :(

I create attachment to show you my problem with zero.

http://files.engineering.com/getfile.aspx?folder=e7bf50c5-00e9-4d03-8263-30

pstuckey (Electrical) · Answer 6 · 2008-04-01 18:15:04

One possibility would be to set the "undefined" value to something out of range, then manually set your z axis so this range is not shown. For instance in your plot on the upper left: set the undefined value to be -1 (rather than 0), then left click the graph, select properties, uncheck auto scale z axis, then set the z axis limits to 0 and 10.

Peter

philipoakley (Aerospace) · Answer 7 · 2008-04-04 04:35:28

If you save as V11 format (.mcd) then more folk can read it.

There are still a large community who are sticking at V11 until V14/15 becomes more stable and efficient.

V14 is good for pro/e integration but still has a couple of rough edges for those using symbolics [has new MuPad engine].

Philip

Briscoz (Computer) · Answer 8 · 2008-04-07 06:55:31

When I used NaN, then symbol below the graf become red.
I tried manually set the range but this was without effect :(

I saved it into a test.mcd W11 file

http://files.engineering.com/getfile.aspx?folder=0fdde483-c62d-4d55-b1ff-20

philipoakley (Aerospace) · Answer 9 · 2008-04-08 12:26:24

I'm getting a set of plots in V11.

What am I looking for that isn't working?

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"IF" function with undefined "OTHERWISE" item?