[R] How to extract one of four plots in a linear regression model

FMH kagba2006 at yahoo.com
Thu Feb 25 16:50:24 CET 2010

Dear All,

A linear regression model could be fitted by using lm function and the plot function can be used to check the assumption of the model. 

The help menu shows few instances on suitable coding for fitting such a linear model. In addition, four different plots could be extracted simultaneously with only a single plot function as followed:

## Annette Dobson (1990) "An Introduction to Generalized Linear Models".
## Page 9: Plant Weight Data.
ctl <- c(4.17,5.58,5.18,6.11,4.50,4.61,5.17,4.53,5.33,5.14)
trt <- c(4.81,4.17,4.41,3.59,5.87,3.83,6.03,4.89,4.32,4.69)
group <- gl(2,10,20, labels=c("Ctl","Trt"))
weight <- c(ctl, trt)
anova(lm.D9 <- lm(weight ~ group))
opar <- par(mfrow = c(2,2), oma = c(0, 0, 1.1, 0))
plot(lm.D9, las = 1)     

The plot function gives four different plots simulaneously but i just need only part of them, for instance the normality plot. Could someone  give some ideas the way to extract this single plot as i need to copy only this plot and paste it into Word document.


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