On 5/6/2008 12:07 PM, Dr. Ottorino-Luca Pantani wrote:
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 ?
I believe this function matches the description in OOO:
mround <- function(number, multiple) multiple * round(number/multiple)
Duncan Murdoch
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