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

[rezvan hatami]

For the sake of simplicity, I use my example to explain what I have written:


nutrient<-lm(nitrate~0.9*fertilizer-0.02*flowrate+0.5*rain)

datafram=data1


Change the value of fertelizer--à datafram=data2


predict(lm(nitrate~0.9*fertilizer2-0.02*flowrate+0.5*rain), datafram=data2

Is that better now?


      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, 10:28
 Subject: Re: [R] How I can calculate the value of response variable
   
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,flowratespring,site1,0.2,2,1spring,site2,1.2,3,1spring,site3,2.2,5,2summer,site1,3.2,1,2summer,site2,4.2,2,2summer,site3,5.2,3,2fall,site1,6.2,4,3fall,site2,7.2,5,3fall,site3,8.2,6,3winter,site1,9.2,4,4winter,site2,10.2,8,4winter,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 JimThank 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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