(https://bugs.r-project.org/bugzilla3/show_bug.cgi?id767), but

Prof. Ripley says I'm premature, and I should raise the question here.

Here's the behavior I assert is a bug:

The output from delete.response on a terms object alters the formula

by removing the dependent variable. It removes the response from the

"variables" attribute and it changes the response attribute from 1 to

0. The response is removed from "predvars"

But it leaves the name of the dependent variable first in the in

"dataClasses". It caused an unexpected behavior in my code, so (as

usual) the bug may be mine, but in my heart, I believe it belongs to

delete.response.

To illustrate, here's a terms object from a regression.

tt

y ~ x1 * x2 + x3 + x4attr(,"variables")

list(y, x1, x2, x3, x4)

attr(,"factors")

x1 x2 x3 x4 x1:x2

y 0 0 0 0 0

x1 1 0 0 0 1

x2 0 1 0 0 1

x3 0 0 1 0 0

x4 0 0 0 1 0

attr(,"term.labels")

[1] "x1" "x2" "x3" "x4" "x1:x2"

attr(,"order")

[1] 1 1 1 1 2

attr(,"intercept")

[1] 1

attr(,"response")

[1] 1

attr(,".Environment")

<environment: R_GlobalEnv>

attr(,"predvars")

list(y, x1, x2, x3, x4)

attr(,"dataClasses")

y x1 x2 x3 x4

"numeric" "numeric" "numeric" "numeric" "numeric"

Now observe that delete.response removes the response from all

attributes except dataClasses.

delete.response(tt)

~x1 * x2 + x3 + x4attr(,"variables")

list(x1, x2, x3, x4)

attr(,"factors")

x1 x2 x3 x4 x1:x2

x1 1 0 0 0 1

x2 0 1 0 0 1

x3 0 0 1 0 0

x4 0 0 0 1 0

attr(,"term.labels")

[1] "x1" "x2" "x3" "x4" "x1:x2"

attr(,"order")

[1] 1 1 1 1 2

attr(,"intercept")

[1] 1

attr(,"response")

[1] 0

attr(,".Environment")

<environment: R_GlobalEnv>

attr(,"predvars")

list(x1, x2, x3, x4)

attr(,"dataClasses")

y x1 x2 x3 x4

"numeric" "numeric" "numeric" "numeric" "numeric"

pj

--

Paul E. Johnson

Professor, Political Science

1541 Lilac Lane, Room 504

University of Kansas