David.
>> 12/31/2015 (25 observations) and the other dataset (leafbiom) is
>> recorded from 10/7/2009 to 12/29/2016 (daily observations).
>>
>> I want to use the 25 observations of stand height to predict the daily
>> stand height from 10/7/2009 to 12/29/2016. The daily stand height will
>> be multiplied by leaf biomass to produce a new variable.
>>
>> I agree that a loop is not needed, would the forecast library help or
>> should I use predict library.
>>
>> Stand_Height=ts(Stand_Height$height,start=2009,end = 2016,
>> frequency =365)
>>
>> plot(forecast(ets(Stand_Height),10))
>> a=seq(as.Date("2009-12-01"),by="weeks",length=11)
>> axis(1, at = a, labels = format(a, "%Y %b %d"), cex.axis=0.6)
>>
>>
>> #Error :$ operator is invalid for atomic vectors
>>
>> Thanks
>>
>>
>> Ahmed Attia, Ph.D.
>> Agronomist & Soil Scientist
>>
>>
>>
>>
>>
>>
>> On Fri, Jun 30, 2017 at 10:37 AM, Sarah Goslee <sarah.goslee at gmail.com> wrote:
>>> There are a bunch of things wrong here, although without a
>>> reproducible example I can't really fix most of them.
>>>
>>> - You're overwriting SH within the loop.
>>> - You're running the regression 2641 times, even though the result
>>> never changes.
>>> - You're never predicting from your linear model using the other data
>>> not in the regression.
>>> - Leaf biomass data is never used for anything. I would have thought
>>> that you would use leaf biomass as the predictor variable, not Date.
>>> - I'm not sure why you want the cumulative sum of stand height; that
>>> doesn't make sense to me.
>>>
>>> I'm guessing you want:
>>>
>>> height.model <- lm(height ~ leafbiomass, data = Stand_Height)
>>> pred.height <- predict(height.model, leafbiom)
>>>
>>> # not sure about the reasoning behind this
>>> SH <- cumsum(pred.height)
>>>
>>> You don't need a loop. Overwriting SH is the biggest R problem; the
>>> rest of my questions have to do with what your objective actually is,
>>> like what you are modeling and what you are doing with the
>>> predictions. But my sample code might be enough to get you headed in
>>> the right direction regardless.
>>>
>>> Sarah
>>>
>>> On Fri, Jun 30, 2017 at 9:27 AM, Ahmed Attia <ahmedatia80 at gmail.com> wrote:
>>>> Hi folks,
>>>>
>>>> I have 25 stand height observations over 7 years period and daily
>>>> leafbiomass data during this period. I want to use the 25 plant height
>>>> observations as inputs and predict the daily stand height during the 7
>>>> years.
>>>>
>>>>
>>>> SH=matrix(data=NA , nrow = 2641, ncol = 1)
>>>> for (i in 1:2641) {
>>>> SH<- predict(lm(height~Date, data=Stand_Height));
>>>>
>>>> dl=leafbiom$Date[i-1];
>>>> de=leafbiom$Date[i];
>>>> SH[i]=sum(SH[leafbiom$Date==de&leafbiom$Date==dl])
>>>>
>>>>
>>>> }
>>>> SH
>>>>
>>>>
>>>> The SH output is the prediction of Stand height in 25 observations
>>>> only and provides NA for the remaining 2616 iterations.
>>>>
>>>> Thanks for your help.
>
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David Winsemius
Alameda, CA, USA