[R] About lm()

[John Fox]

Dear Marcelo,

Apparently f1 is an ordered factor rather than a factor; consequently 
orthogonal polynomial contrasts are generated. Type ?contr.poly for more 
information.

Alternatively, you may have changed the contrast option for unordered 
factors to contr.poly, but this seems unlikely. Enter options('contrasts') 
to check the contrasts option. You can enter class(f1) to check whether f1 
is a factor or an ordered factor.

I hope that this helps,
  John

At 06:30 PM 8/20/2002 -0300, marcelo wrote:
>Dear Mr. and Mrs.
>
>I'm very grateful for these software and this list.
>My question is:
>when a use linear multiple regression (lm()) for my data,
>abundance ichthyoplankton ~ salinity + temperature + month of the
>year(f1 is a factor: 1 for january, 2 for february, ..., 12 for december),
>the summary() of results is
>...
>Coefficients:
>                  Estimate Std. Error t value Pr(>|t|)
>(Intercept)       0.726347   0.285607   2.543 0.011217 *
>temperature     -0.011410   0.014200  -0.804 0.421978
>salinity        -0.018194   0.002453  -7.416 3.81e-13 ***
>f1.L             -0.060886   0.093818  -0.649 0.516584
>f1.Q              0.856714   0.196832   4.353 1.56e-05 ***
>f1.C              0.522526   0.078261   6.677 5.27e-11 ***
>f1^4              0.570152   0.095059   5.998 3.33e-09 ***
>f1^5             -0.292748   0.077436  -3.781 0.000171 ***
>...
>f1^10             0.182789   0.082543   2.214 0.027145 *
>f1^11             0.329844   0.094470   3.492 0.000513 ***
>
>What does mean f1.L, f1.Q, f1.C ??
>Thanks in advance.
>--
>Marcelo Alexandre Bruno - Pos-graduacao Oceanografia Biologica
>Departamento de Oceanografia -  Laboratorio de Ecologia do Ictioplancton
>(0xx53) 2336529 - Rio Grande - RS - BRAZIL

-----------------------------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox at mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox
-----------------------------------------------------

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