# [R] Loop question?

Jeff Newmiller jdnewmil at dcn.davis.CA.us
Sat Jan 26 08:09:48 CET 2013

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In general, you can use expand.grid to generate all combinations of inputs, compute results as a vector just as long as the expand.grid data frame has rows, and identify which results meet your criteria by a logical test, and use that test to identify which input combinations worked.
Provide a working starting point and someone might give you working code as an answer. (where do a and b come into your problem?)
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Andras Farkas <motyocska at yahoo.com> wrote:

>Dear All
>�
>I have the following data (somewhat simplyfied):
>�
>TINF <-1
>a <-c(500,750,1000,1250,1500,1750,2000)
>b <-c(8,12,18,24,36,48,60,72,96)
>�
>following function:
>�
>infcprodessa <-function (D, tin, tau, ts)
>� (D * (1 - exp(-0.048 * tin))/(tin * (0.048*79) * (1 - exp(-0.048 *
>tau)))) * exp(-0.048 * (ts - tin))
>
>z <-sapply(1:1, function(n) infcprodessa(1000,TINF,12,12-TINF))
>�
>is there a way to select the combination of respective a and b values
>that would result in a calculated z that is between 15 and 20? In this
>case the a would be 1000 and the b would be 12 (other combinations are
>also possible), but how could I automatically find them? perhaps a
>loop?
>�
>Apreciate the help,
>�
>Sincerely,
>�
>Andras
>	[[alternative HTML version deleted]]
>
>
>
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