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 ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
