[R] How to coerce a parameter in nls?

[Jeff Newmiller]

Why not rewrite the function so that value is not a parameter?
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Sent from my phone. Please excuse my brevity.

On September 18, 2015 9:54:54 PM PDT, Jianling Fan <fanjianling at gmail.com> wrote:
>Hello, everyone,
>
>I am using a nls regression with 6 groups data. I am trying to coerce
>a parameter to 1 by using a upper and lower statement. but I always
>get an error like below:
>
>Error in ifelse(internalPars < upper, 1, -1) :
>  (list) object cannot be coerced to type 'double'
>
>does anyone know how to fix it?
>
>thanks in advance!
>
>My code is below:
>
>
>
>> dproot
>   depth       den ref
>1     20 0.5730000   1
>2     40 0.7800000   1
>3     60 0.9470000   1
>4     80 0.9900000   1
>5    100 1.0000000   1
>6     10 0.6000000   2
>7     20 0.8200000   2
>8     30 0.9300000   2
>9     40 1.0000000   2
>10    20 0.4800000   3
>11    40 0.7340000   3
>12    60 0.9610000   3
>13    80 0.9980000   3
>14   100 1.0000000   3
>15    20 3.2083491   4
>16    40 4.9683383   4
>17    60 6.2381133   4
>18    80 6.5322348   4
>19   100 6.5780660   4
>20   120 6.6032064   4
>21    20 0.6140000   5
>22    40 0.8270000   5
>23    60 0.9500000   5
>24    80 0.9950000   5
>25   100 1.0000000   5
>26    20 0.4345774   6
>27    40 0.6654726   6
>28    60 0.8480684   6
>29    80 0.9268951   6
>30   100 0.9723207   6
>31   120 0.9939966   6
>32   140 0.9992400   6
>
>> fitdp<-nls(den~Rm[ref]/(1+(depth/d50)^c),data=dproot,
>+ start = list(Rm=c(1.01, 1.01, 1.01, 6.65,1.01,1), d50=20, c=-1))
>> summary(fitdp)
>
>Formula: den ~ Rm[ref]/(1 + (depth/d50)^c)
>
>Parameters:
>    Estimate Std. Error t value Pr(>|t|)
>Rm1  1.12560    0.07156   15.73 3.84e-14 ***
>Rm2  1.57643    0.11722   13.45 1.14e-12 ***
>Rm3  1.10697    0.07130   15.53 5.11e-14 ***
>Rm4  7.23925    0.20788   34.83  < 2e-16 ***
>Rm5  1.14516    0.07184   15.94 2.87e-14 ***
>Rm6  1.03658    0.05664   18.30 1.33e-15 ***
>d50 22.69426    1.03855   21.85  < 2e-16 ***
>c   -1.59796    0.15589  -10.25 3.02e-10 ***
>---
>Signif. codes:  0 ?**?0.001 ?*?0.01 ??0.05 ??0.1 ??1
>
>Residual standard error: 0.1094 on 24 degrees of freedom
>
>Number of iterations to convergence: 8
>Achieved convergence tolerance: 9.374e-06
>
>> fitdp1<-nls(den~Rm[ref]/(1+(depth/d50)^c),data=dproot,
>algorithm="port",
>+ start = list(Rm=c(1.01, 1.01, 1.01, 6.65, 1.01, 1), d50=20, c=-1),
>+ lower = list(Rm=c(1.01, 1.01, 1.01, 6.65, 1.01, 1), d50=20, c=-1),
>+ upper = list(Rm=c(2.1, 2.2, 2.12, 12.5, 2.3, 1), d50=50, c=1))
>
>Error in ifelse(internalPars < upper, 1, -1) :
>  (list) object cannot be coerced to type 'double'
>
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