[R] Is there in R a function equivalent to the mround, as found in most spreadsheets?

[Dr. Ottorino-Luca Pantani]

Dear R-users,
I have the following problem

In a lab experiment I have to mix three solutions to get different 
concentrations of various molecules in a cuvette

I've used R to calculate the necessary µliters for each of the level of 
the experiment and I must confess that it is more useful and easier to 
achieve the results than using spreadsheets.

But there's a problem.

Imagine that for a particular cuvette (I have 112 different cuvettes !!) 
you have to mix the following volumes of solution A, B, and C respectively.

c(1803.02, 193.51, 3.47)

Each solution is to be taken with 3 different pipettes (5000, 250 and 10 
µL Volume max) and each of those delivers volumes in steps of 50 µL,  5 
µL  or 1µL, respectively
Since the above values  would eventually become

c(1800, 195, 3)

it is then necessary to recalculate all the final concentrations
of A, B and C, because the volumes are changed.


I know that in most spreadsheets (Calc in Open Office, Gnumeric, Excel 
and so on)
there's a function such as

mround(num; num)

that give the results I need, but I want to learn more on R functions.


I played a little with R functions such as

round, signif, ceiling, trunc, and floor

but without success.
Any hint to solve this problem ?

Thanks a lot

http://www.openofficetips.com/blog/archives/2005/04/rounding_to_the.html
http://www.gnome.org/projects/gnumeric/doc/gnumeric-MROUND.shtml

-- 
Ottorino-Luca Pantani, Università di Firenze
Dip. Scienza del Suolo e Nutrizione della Pianta
P.zle Cascine 28 50144 Firenze Italia
Tel 39 055 3288 202 (348 lab) Fax 39 055 333 273 
OLPantani at unifi.it  http://www4.unifi.it/dssnp/