I feel bad even asking, but:
Rgames> data(OrchardSprays)
Rgames> model<-lm(decrease~.,data=OrchardSprays)
Rgames> model
Call:
lm(formula = decrease ~ ., data = OrchardSprays)
Coefficients:
(Intercept) rowpos colpos treatmentB treatmentC
22.705 -2.784 -1.234 3.000 20.625
treatmentD treatmentE treatmentF treatmentG treatmentH
30.375 58.500 64.375 63.875 85.625
Rgames> levels(OrchardSprays$treatment) #just double-checking...
[1] "A" "B" "C" "D" "E" "F" "G" "H"
So: why isn't there a value for the level "A" of treatment? Is it
because the (alphabetically) first level is treated as the control?
And if so, what should I do (calculate) with the coefficients to compare
them with the statistics of the data subset with level "A" ?
Please feel free to tell me to shut up and read some part of R-inferno
or other helpful document.
Thanks.
Carl
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