I have the following data set, and I have to find the line of best fit using this equation, y = a*(1 - exp(-b*x)). samples = seq(1,20,by=1) species = c(5,8,9,9,11,11,12,15,17,19,20,20,21,23,23,25,25,27,27,27) plot(samples,species, main = "Accumulation Curve for Tree Species Richness", xlab = "Samples", ylab = "Number of Species") curve((y = 27*(1 - exp(-.15*x))),from=0,to=20,add = T) I tried to find the best fit curve using: fit = nls(species ~ a *(1 - exp(-b*x)),start = list(a = 27, b = .15) but I get a "parameters without starting value in 'data': x" and I don't have any idea what this means, or how to fix the above code. -- View this message in context: http://r.789695.n4.nabble.com/Generating-a-best-fit-line-for-non-linear-data-tp3482193p3482193.html Sent from the R help mailing list archive at Nabble.com.
Generating a best fit line for non linear data
3 messages · BornSurvivor, Jorge Ivan Velez, Andrew Robinson
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I think that you probably need to provide the x values to nls. Try, for example, fit <- nls(species ~ a *(1 - exp(-b*samples)),start = list(a = 27, b = .15)) I hope that this helps, Andrew
On Thu, Apr 28, 2011 at 01:56:43PM -0700, BornSurvivor wrote:
I have the following data set, and I have to find the line of best fit using this equation, y = a*(1 - exp(-b*x)). samples = seq(1,20,by=1) species = c(5,8,9,9,11,11,12,15,17,19,20,20,21,23,23,25,25,27,27,27) plot(samples,species, main = "Accumulation Curve for Tree Species Richness", xlab = "Samples", ylab = "Number of Species") curve((y = 27*(1 - exp(-.15*x))),from=0,to=20,add = T) I tried to find the best fit curve using: fit = nls(species ~ a *(1 - exp(-b*x)),start = list(a = 27, b = .15) but I get a "parameters without starting value in 'data': x" and I don't have any idea what this means, or how to fix the above code. -- View this message in context: http://r.789695.n4.nabble.com/Generating-a-best-fit-line-for-non-linear-data-tp3482193p3482193.html Sent from the R help mailing list archive at Nabble.com.
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