[R] Problems with abline adding regression line to a graph

[CG Pettersson]

Hello all,

R2.1.1, W2k

I try to make a plot of a simple regression model in this way:

 > with(njfA_bcd, {
+ plot(TC_OS.G31,Prot,cex = 2, col = "red", xlab= "TC/OS at GS32",
+ ylab="Grain crude protein (CP)")
+ })

This part works well and produces the datapoints as red circles.
When I try to add a line, using a fitted linear model in a way
that works perfect with other variables in the same dateset the
following happens:

 > with(njfA_bcd, {
+    abline(lm(predict(m1tc) ~ TC_OS.G31), lty = 1, col = "red")
+ })
Error in model.frame(formula, rownames, variables, varnames, extras, 
extranames,  :
        variable lengths differ

And this means?

There exists missing values for TC_OS.G31 in the dataset. From the 
beginning
m1tc was a lm() object, which gave the same Error message. To try to fix the
problem I changed to lme() and used na.action=na.omit explicitely, but this
didn´t help.

Here is the summary of m1tc:

 > summary(m1tc)
Linear mixed-effects model fit by REML
 Data: njfA_bcd
       AIC      BIC    logLik
  209.4914 219.0692 -100.7457

Random effects:
 Formula: ~1 | Trial
        (Intercept)  Residual
StdDev:    1.242184 0.6520464

Fixed effects: Prot ~ TC_OS.G31
                Value Std.Error DF   t-value p-value
(Intercept)  14.86209  0.957630 68 15.519662       0
TC_OS.G31   -24.22286  4.792801 68 -5.054008       0
 Correlation:
          (Intr)
TC_OS.G31 -0.935

Standardized Within-Group Residuals:
        Min          Q1         Med          Q3         Max
-1.68329774 -0.73751040 -0.05600477  0.68301243  2.21693174

Number of Observations: 83
Number of Groups: 14
 >

What is happening and what shall I do about it?

Cheers
/CG

-- 
CG Pettersson, MSci, PhD Stud.
Swedish University of Agricultural Sciences (SLU)
Dept. of Crop Production Ecology. Box 7043.
SE-750 07 UPPSALA, Sweden.
+46 18 671428, +46 70 3306685
cg.pettersson at evp.slu.se