R help - Jul 2008 - lines() warning message

I have data that looks like

Year,Recruit,Spawner,Mtempcv
1958,4532,775,0.24125
1959,22996,2310,0.16319
1960,628,2990,0.46056
1961,879,1400,0.33028
1962,14747,1130,0.22618
1963,13205,790,0.20596
1964,31793,1195,0.19229
1965,10621,981,0.20363
1966,22271,870,0.3452
1967,8736,1104,0.27511
1968,8761,883,0.10884
1969,18885,1421,0.17799
1970,10098,1198,0.2106
1971,3394,760,0.22098
1972,1697,1354,0.39461
1973,25159,1308,0.19696
[truncated]

with program

#Ricker Curve
mod2=nls(Recruit~(Spawner*exp((delta+echo*Spawner)+(foxtrot*Mtempcv))),
data=box48,
    start=list(delta=4, echo=0, foxtrot=-7), trace=TRUE)
plot(Recruit~Spawner, data=box48, pch=19)
mod2a=seq(369, 3000)
lines(mod2a, predict(mod2, list(Spawner=mod2a)), col="red", lty=2)

R has no problem finding a solution to the nls() model (only 7 iterations are
needed), but when I try to plot the line on the requested plot, I get the
warning message "Warning message:
In (delta + echo * Spawner) + (foxtrot * Mtempcv) :
  longer object length is not a multiple of shorter object length."

R tries to plot the line, but it appears as just a mess of vertical lines that
get more dense where (I would imagine) the actual line is to go.  Any ideas what
may be causing this issue?

Thanks for your help, 

SR

Steven H. Ranney
Graduate Research Assistant (Ph.D)
USGS Montana Cooperative Fishery Research Unit
Montana State University
PO Box 173460
Bozeman, MT 59717-3460

phone: (406) 994-6643
fax:   (406) 994-7479


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Ranney, Steven wrote:
> I have data that looks like
>
> Year,Recruit,Spawner,Mtempcv
> 1958,4532,775,0.24125
> 1959,22996,2310,0.16319
> 1960,628,2990,0.46056
> 1961,879,1400,0.33028
> 1962,14747,1130,0.22618
> 1963,13205,790,0.20596
> 1964,31793,1195,0.19229
> 1965,10621,981,0.20363
> 1966,22271,870,0.3452
> 1967,8736,1104,0.27511
> 1968,8761,883,0.10884
> 1969,18885,1421,0.17799
> 1970,10098,1198,0.2106
> 1971,3394,760,0.22098
> 1972,1697,1354,0.39461
> 1973,25159,1308,0.19696
> [truncated]
>
> with program
>
> #Ricker Curve
> mod2=nls(Recruit~(Spawner*exp((delta+echo*Spawner)+(foxtrot*Mtempcv))),
data=box48,
>     start=list(delta=4, echo=0, foxtrot=-7), trace=TRUE)
> plot(Recruit~Spawner, data=box48, pch=19)
> mod2a=seq(369, 3000)
> lines(mod2a, predict(mod2, list(Spawner=mod2a)), col="red",
lty=2)
>
> R has no problem finding a solution to the nls() model (only 7 iterations
are needed), but when I try to plot the line on the requested plot, I get the
warning message "Warning message:
> In (delta + echo * Spawner) + (foxtrot * Mtempcv) :
>   longer object length is not a multiple of shorter object length."
>
> R tries to plot the line, but it appears as just a mess of vertical lines
that get more dense where (I would imagine) the actual line is to go.  Any ideas
what may be causing this issue?
>
>   
Hmm,,, The predict() call looks dodgy. The model depends on Spawner AND 
Mtempcv, but you're only giving the former in the newdata= part. So a 
good guess that one of them is recycled to the length of the other.

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