On May 9, 2008, at 5:39 AM, Dieter Menne wrote:
Dr. Ottorino-Luca Pantani <ottorino-luca.pantani <at> unifi.it>
writes:
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
If I understand the OP's question properly, the first value is to be
a multiple of 50, the second a multiple of 5, and the third a
multiple of 1. This can be done with this slight variation on the
above theme:
a <- c(1803.02, 193.51, 3.47)
b <- c(50,5,1)
round(a/b) *b
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
Haris Skiadas
Department of Mathematics and Computer Science
Hanover College
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