R help - May 2010 - how to remove interactions of factor with continuous var

I need to remove certain interactions and keep only the one between the second
level of the factor and the continuous var t2

bin4 <- glm(resp2~
t*t2+c5.vrm,data=dfa,family="quasibinomial")
> summary(bin4)
Call:
glm(formula = resp2 ~ t * t2 + c5.vrm, family = "quasibinomial",
    data = dfa)

Deviance Residuals:
    Min       1Q   Median       3Q      Max
-6.5464  -3.0720  -1.8135   0.4896  28.9207

Coefficients:
             Estimate Std. Error t value Pr(>|t|)
(Intercept) -1.492379   0.147779 -10.099  < 2e-16 ***
t2           1.381409   0.193110   7.153 1.19e-11 ***
t3           0.223979   0.275389   0.813 0.416898
t4          -1.751518   0.495391  -3.536 0.000494 ***
t5          -2.455172   0.913674  -2.687 0.007747 **
t6          -2.347207   1.131134  -2.075 0.039120 *
t2          -0.030819   0.013144  -2.345 0.019914 *
c5.vrm       0.427088   0.140085   3.049 0.002574 **
t2:t2       -0.015909   0.007292  -2.182 0.030174 *
t3:t2       -0.016170   0.010479  -1.543 0.124218
t4:t2        0.024352   0.016900   1.441 0.151009
t5:t2       -0.012071   0.034230  -0.353 0.724680
t6:t2       -0.041797   0.047106  -0.887 0.375880
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05
'.' 0.1 ' ' 1

(Dispersion parameter for quasibinomial family taken to be 41.75819)

Trying with - t3:t2 etc did not work neither did putting quotes around the
terms.
I need to have the continuous var c5.vrm same for all levels of the factor so
estimating separate equations for each level will not work. I could use offset,
but seems quite an ugly solution, there should be a way to specify exactly which
interactions are desired.
Thank you all.

Stephen Bond


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