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

[Dieter Menne]

Dr. Ottorino-Luca Pantani <ottorino-luca.pantani <at> unifi.it> writes:

> 
> 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.

A first guess would be

a = c(1803.02, 193.51, 3.47)
round(a / 5)*5

which gives

1805  195    5

This is not exactly what you want, but it shows that the problem is a bit
ill-defined. In the example you gave, why do you want 1800, and not 1805, which
is possible with the pipettes? I assume that you laboratory experience is
working in the background, telling you to stop pipetmanning when you are close
to the result in some "percentage" feeling.

Dieter