[R] Asking for help

[Boris Steipe]

What about the advice I sent you this morning?


B.


> On Apr 19, 2017, at 1:49 PM, Boris Steipe <boris.steipe at utoronto.ca> wrote:
> 
> No attachments please. Use the dput() function. And keep the correspondence on the list, there are many colleagues who are far more knowledgeable than I am.
> 
> Cheers,
> Boris
> 
> 
> 
> 
>> On Apr 19, 2017, at 1:47 PM, Santiago Bueno <swbueno at gmail.com> wrote:
>> 
>> Thanks a lot Mr. Steipe. I have attached to this email an Excel file with 48 observations.  The problem is that when I try to get the prediction plot for the following model:
>> start <- coef (lm(log(Btot)~I(log(dbh**2*haut)),data=dat[dat$Btot>0,]))
>> start[1] <- exp(start[1])
>> names(start) <- c("a","b")
>> model18 <- nls(Btot~a*(dbh**2*haut)**b,data=dat,start=start,weights=1/dat$dbh**4)
>> summary(model18)
>> 
>> using this code:
>> 
>> with(dat,plot(dbh**2*haut,Btot,xlab="dbh^2*H(cm^2.m)",ylab="Biomass (t)", pch=19))
>> D <- seq(0,180,length=20)
>> H <- seq(0,61,length=20)
>> 
>> abline(model18, lwd=3)
>> 
>> I get the data points but not the prediction line (see below)
>> 
>> <image.png>
>> If you can help me in getting this line, I will be eternaly grateful..
>> 
>> Best regards,
>> 
>> Santiago Bueno
>> 
>> On Wed, Apr 19, 2017 at 12:20 PM, Boris Steipe <boris.steipe at utoronto.ca> wrote:
>> Can you provide a small reproducible example and explain what exactly is going wrong?
>> 
>> Just a handful of data points will do.
>> 
>> 
>> B.
>> 
>> 
>> 
>>> On Apr 18, 2017, at 2:16 PM, Santiago Bueno <swbueno at gmail.com> wrote:
>>> 
>>> Thanks Boris, the following is an extract of my data. I have developed
>>> biomass models using codes like:
>>> 
>>> start <- coef (lm(log(Btot)~I(log(dbh**2*haut)),data=dat[dat$Btot>0,]))
>>> 
>>> start[1] <- exp(start[1])
>>> 
>>> names(start) <- c("a","b")
>>> 
>>> M1 <- nls(Btot~a*(dbh**2*haut)**b,data=dat,start=start,weights=1/dat$dbh**4)
>>> 
>>> 
>>> start <- coef(lm(log(Btot)~I(log(dbh))+I(log(haut)),data=dat[dat$Btot>0,]))
>>> 
>>> start[1] <- exp(start[1])
>>> 
>>> names(start) <- c("a","b1","b2")
>>> 
>>> M2 <- nls(Btot~a*dbh**b1*haut**b2,data=dat,start=start,weights=1/dat$dbh**4)
>>> 
>>> 
>>> Tree No dbh haut Btot
>>> 1 35.00 18.90 0.535
>>> 2 25.00 16.60 0.248
>>> 3 23.00 19.50 0.228
>>> 4 13.50 15.60 0.080
>>> 5 20.00 18.80 0.172
>>> 6 23.00 17.40 0.190
>>> 7 29.00 19.90 0.559
>>> 8 17.60 18.20 0.117
>>> 9 31.00 25.30 0.645
>>> 10 26.00 23.50 0.394
>>> 11 13.00 13.00 0.038
>>> 12 32.00 20.70 0.443
>>> It is my interest to get prediction plots for the models. I have tried to
>>> use the following codes with no success: Let m be one of the fitted models
>>> with dbh as the only entry. To construct a plot of the predictions made by
>>> this model I have tried:
>>> with(dat,plot(dbh,Btot,xlab="Dbh(cm)",ylab="Biomass (t)"))
>>> D <- seq(par("usr")[1],par("usr")[2],length=200)
>>> lines(D,predict(m,newdata=data.frame(dbh=D)),col="red")
>>> For a model m that has dbh and height as entries, I have tried to get its
>>> predictions as follows:
>>> D <- seq(0,180,length=20)
>>> H <- seq(0,61,length=20)
>>> B <- matrix(predict(m,newdata=expand.grid(dbh=D,height=H)),length(D))
>>> 
>>> Can someone provide help please!!!
>>> 
>>> 
>>> Best regards,
>>> 
>>> Santiago Bueno
>>> 
>>>      [[alternative HTML version deleted]]
>>> 
>>> ______________________________________________
>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>> 
>> 
>> <Biomasa_Total.xls>
> 

> On Apr 19, 2017, at 4:13 PM, Ista Zahn <istazahn at gmail.com> wrote:
> 
> For help in formulating your question in a way that makes it easy to
> help you see http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example
> 
> When asking for help on the R-help mailing list in particular, make
> sure to send plain-text email.
> 
> Best,
> Ista
> 
> On Wed, Apr 19, 2017 at 3:56 PM, Santiago Bueno <swbueno at gmail.com> wrote:
>> I have tried to ask for help ragarding R software but it seems that I do
>> not know how to send my questions. Can someone "PLEASE" tutor me on how to
>> structure my messages?
>> 
>> Best regards,
>> 
>> Santiago
>> 
>>        [[alternative HTML version deleted]]
>> 
>> ______________________________________________
>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.