From: Dieter Menne <dieter.menne_at_menne-biomed.de>

Date: Fri, 09 May 2008 09:39:17 +0000 (UTC)

R-help_at_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. Received on Fri 09 May 2008 - 09:42:52 GMT

Date: Fri, 09 May 2008 09:39:17 +0000 (UTC)

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 = c(1803.02, 193.51, 3.47)

round(a / 5)*5

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.

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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. Received on Fri 09 May 2008 - 09:42:52 GMT

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