[R] How I can calculate the value of response variable

[Jim Lemon]

Hi Rezvan,
This looks like a simple problem of solving linear equations (and very much
like a homework exercise). Therefore I won't actually give you the answer,
but suggest the steps for the solution. First you have to get the data into
R, so here is one way:

rhdat<-read.table(text="season,site,nitrate,fertilizer1,flowrate
spring,site1,0.2,2,1
spring,site2,1.2,3,1
spring,site3,2.2,5,2
summer,site1,3.2,1,2
summer,site2,4.2,2,2
summer,site3,5.2,3,2
fall,site1,6.2,4,3
fall,site2,7.2,5,3
fall,site3,8.2,6,3
winter,site1,9.2,4,4
winter,site2,10.2,8,4
winter,site3,11.2,9,4",sep=",",header=TRUE)

You now have a data frame (rhdat) containing the values in your table.

1) calculate values for rain, which are missing from the table, e.g.

rhdat$rain<-2*(rhdat$nitrate-0.9*rhdat$fertilizer+0.02*rhdat$flowrate)

the above is an R expression to calculate the values for rain.

2) You may want explicitly calculate new values for rhdat$fertilizer, and
you have indicated that you already know how to do that. The above should
give you enough information about R syntax to translate the simple equation.

3) Now calculate new values for nitrate based on the equation you supplied,
but substituting the calculated values for rain and the modified values for
fertilizer.

Jim


On Mon, Jun 27, 2016 at 9:43 AM, rezvan hatami <rezvan.hatami_iut at yahoo.com>
wrote:

> Hi Jim
> Thank you for your answer. nitrate=0.9*fertilizer-0.02*flowrate+0.5*rain
>
> my matrix:
> season site nitrate fertilizer1 flow rate
> spring site1 0.2 2 1
> spring site2 1.2 3 1
> spring site3 2.2 5 2
> summer site1 3.2 1 2
> summer site2 4.2 2 2
> summer site3 5.2 3 2
> fall site1 6.2 4 3
> fall site2 7.2 5 3
> fall site3 8.2 6 3
> winter site1 9.2 4 4
> winter site2 10.2 8 4
> winter site3 11.2 9 4
>
> I would like to know, what will be the values for variable "nitrate" if I
> divide the values of fertilizer by half and change the equation to:
>
> nitrate=0.9*fertilizer2-0.02*flowrate+0.5*rain
>
> in a matrix like:
>
> season site nitrate fertilizer2 flow rate
> spring site1 0.2 1 1
> spring site2 1.2 1.5 1
> spring site3 2.2 2.5 2
> summer site1 3.2 0.5 2
> summer site2 4.2 1 2
> summer site3 5.2 1.5 2
> fall site1 6.2 2 3
> fall site2 7.2 2.5 3
> fall site3 8.2 3 3
> winter site1 9.2 2 4
> winter site2 10.2 4 4
> winter site3 11.2 4.5 4
> Would you please tell me how I can do this in R?
>
> Cheers
>
> Rezvan
>
>
> ------------------------------
> *From:* Jim Lemon <drjimlemon at gmail.com>
> *To:* rezvan hatami <rezvan.hatami_iut at yahoo.com>; r-help mailing list <
> r-help at r-project.org>
> *Sent:* Monday, 27 June 2016, 8:07
> *Subject:* Re: [R] How I can calculate the value of response variable
>
> Hi Rezvan,
> I'll take a guess that you have been presented with a matrix of
> coefficients. You probably know that a linear model is going to look
> something like this:
>
> Y = ax1 + bx2 + cx3 ...
>
> So I will further guess that you want to infer a distribution of Y
> (the response variable) from more than one set of coefficients. If my
> guesses are correct, then you should be able to send an example that
> shows what you have and what you want to get.
>
> Jim
>
>
> On Sun, Jun 26, 2016 at 8:23 PM, rezvan hatami via R-help
> <r-help at r-project.org> wrote:
> >  How I can calculate the value of response variable in a linear model of
> a matrix of several variables?Can somebody please answer me?
> >
> >
> > Cheers
> > Rezvan Hatami
>
> >        [[alternative HTML version deleted]]
> >
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>
>
>
>

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