I would suggest you work out a way of using CHOOSE (its fast and
non-volatile): this should be reasonably straightforward if your intervals
are equal (you have to be able to convert the interval test to a 1-based
integer).
It will be more concise than the equivalent IF and probably more efficient.

If you can sensibly do the calculation using an excel (non-array) formula
then the formula will almost certainly be faster than a UDF, particularly if
calculation is automatic or called by Excel rather than VBA.

regards
Charles
______________________
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"Tushar Mehta" wrote in message
om...
My guess would be that XL formulas should be very fast. Also, what you
have
isn't overly complicated. I would go this route first. Further, I would
put t mod 1 (or, in XL, MOD(t,1)) into one cell. That way that expression
is calculated only once.

If you consider the UDF route, I would not be surprised if you do not see
any noticable performance difference. And, if you can generate the
results
for a vector of values (t=0,0.05,...0.95, 1) all at once and return them
as
an "array formula" the UDF will be quite fast.

You might also want to check your V(t) for 0.5 < t <= 0.75.
Maybe, you really want 1-4*(0.75-(t mod 1)) but it will go from V(0.5)=0
to
V(0.75)=1. If you are generating a 0-1 pulse with a linear rise and fall,
you need V(t)=4*(0.75-(t mod 1))

--
Regards,

Tushar Mehta
www.tushar-mehta.com
Excel, PowerPoint, and VBA add-ins, tutorials
Custom MS Office productivity solutions

In article .com,
says...
I want to create a function which defines a pulse wave that rises from
0 to 1, stays at one for a bit, lowers to 0, and stays at zero for a
bit.

/ if (t mod 1) <0.25, V(t) = 4* (t mod 1)
| if 0.5 = (t mod 1) 0.25, V(t) = 1
V(t) = |
| if 0.75 =(t mod 1) 0.5, V(t) = 1-4* (0.75-(t mod 1))
\ if 1 (t mod 1) 0.75, V(t) = 0

For this pulse wave there are straight rises, falls and flat bottoms
and tops, which I need (and which is why a sine wave can't be used). If
you're still with me, thanks.

I can either put this all into a long excel equation for each cell that
I want this in (there will be about 4 'if' statements and 6 'mod'
statements) or create a UDF, where the t mod 1 only has to be
calculated once.

Any idea out there how much faster/ slower as UDF really is in a case
like this? Also, can you think of an easier way to create this pulse
wave?

As a side note, the t in my program has some ROW() and COLUMN()
dependence, and there will be 200+ cells filled with this equation
(thus, I can't just compute it once and copy the values to each cell).
Caculation speed is important because each cell is being calculated as
the time, t, is advanced by a timer.

Thanks in advance to anyone who takes a stab at this.

-Abe