Hi Michael,
On Tue, Feb 15, 2011 at 7:15 AM, Michael Pearmain
wrote:
> Hi All,
>
> I'm having some trouble assigning arguments inside a function to
> produce a plot from a model
>
> Can anyone help me? Below I've outlined the situation and examples of
> failing and working code.
>
> Regards
>
> Mike
>
>
>
> ## data ##
>
> decay.data <- ...
>
> behaviors lift reach.uu estimated.conversions.uu total.reach
> 1 1 432.0083 770 770 0.00
> 2 2 432.0083 29660 29660 0.03
> 3 3 429.9864 3 29850 0.03
> 4 4 427.8599 30320 30020 0.03
> 5 5 424.0105 30680 30110 0.03
> 6 6 418.4710 31180 30200 0.03
> 7 7 412.0022 31840 30360 0.03
> 8 8 405.4553 32340 30350 0.03
> 9 9 397.0083 33260 30560 0.03
> 10 10 393.2382 33600 30580 0.03
> 11 11 385.5431 34940 31180 0.03
> 12 12 384.2942 35050 31170 0.03
> 13 13 374.0299 36110 31260 0.03
> 14 14 363.3057 37290 31350 0.03
> 15 15 353.1185 38450 31420 0.03
> 16 16 342.2190 4 31680 0.03
> 17 17 338.9232 40470 31740 0.04
> 18 18 328.8666 41880 31880 0.04
> 19 19 318.3219 45510 33530 0.04
> 20 20 308.1200 47230 33680 0.04
>
> If i use:
>
> library(nlrwr)
> # Build a model.
> decay.model <- nls(lift ~ SSexp(total.reach, y0, b), data = decay.data)
>
> # plot the model
> plot(decay.data[["total.reach"]], decay.data[["lift"]])
> xv <- seq(min(decay.data[["lift"]]), max(decay.data[["total.reach"]]), 0.02)
> yv <- predict(decay.model, newdata = list(total.reach = xv))
> lines(xv,yv)
>
> This works.
Actually it doesn't work for me. I get
xv <- seq(min(decay.data[["lift"]]), max(decay.data[["total.reach"]]), 0.02)
Error in seq.default(min(decay.data[["lift"]]),
max(decay.data[["total.reach"]]), :
wrong sign in 'by' argument
>
> If i try and wrap this in a function and pass the argument values i fail when
> i reach the "list(total.reach = xv)" i've tried various flavours or paste(),
> but again can't figure out where i am going wrong, any help appreciated.
Your example is not reproducible (you don't define the BuildDecayModel
function for us...) which makes it harder to help. But just by
eyeballing...
>
> PlotDecayModel <- function(x = "total.reach",
> y = "lift",
> data) {
>
> decay.model <- BuildDecayModel(x= "total.reach",
Putting "total.reach" in quotes like this just sets x equal to the
text string "total.reach", not to the value of x passed to the
function. If you want the x to be passed from the function remove the
quotes.
> y = "lift",
> data = data)
> # Plot the lift Vs reach plot.
> plot(data[[x]], data[[y]])
> # Add the model curve to the plot.
> xv <- seq(min(data[[x]]), max(data[[x]]), 0.02)
> yv <- predict(decay.model, newdata = list(x = xv))
> lines(xv,yv)
> }
>
> I return the error
> Error in xy.coords(x, y) : 'x' and 'y' lengths differ
>
> I can see this is because the function ignores the 'newdata = list(x = xv)'
> as it is trying ot assign x on the data to be xv,
> (which doesn't exist in the model), so how can i use the arg "total.reach" so
> the argument 'newdata = list(x = xv)' is evaluated as
> 'newdata = list(total.reach = xv)'
I would try something like
nd <- list(xv)
names(nd) <- x
yv <- predict(decay.model, newdata = nd)
>
> Many thanks in advance
HTH, if you still have difficulty please post a reproducible example.
Best,
Ista
>
> Mike
>
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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>
--
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org
__
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
