Re: [Rd] variable scope in update(): bug or feature?

From: Michael <wuolong_at_gmail.com>
Date: Fri 22 Dec 2006 - 17:59:02 GMT

On 22 Dec 2006, Martin Maechler wrote:

> - use a simple reproducible example --
> just for the convenience of your readers

Sending email directly to r-devel doesn't seem to work for me. So I'm resend this via gmane.

Here is an example:

> rm (list = ls())
> x <- 1:10
> mdata <- data.frame (z = rnorm (10), y = x + 3)
> m1 <- lm (y ~ x + z, data = mdata)

> summary (m1)

Call:
lm(formula = y ~ x + z, data = mdata)

Residuals:

      Min 1Q Median 3Q Max -4.950e-16 -8.107e-17 2.085e-17 9.043e-17 3.787e-16

Coefficients:

             Estimate Std. Error    t value Pr(>|t|)
(Intercept)  3.000e+00  1.923e-16  1.560e+16   <2e-16 ***
x            1.000e+00  2.881e-17  3.472e+16   <2e-16 ***
z           -8.717e-17  1.149e-16 -7.590e-01    0.473
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Residual standard error: 2.6e-16 on 7 degrees of freedom
Multiple R-Squared:     1,      Adjusted R-squared:     1
F-statistic: 6.103e+32 on 2 and 7 DF,  p-value: < 2.2e-16


> x <- rep (1:2, each = 5)
> m2 <- update (m1, ~ . - z)
> summary (m2)
Call: lm(formula = y ~ x, data = mdata) Residuals: Min 1Q Median 3Q Max -2.000e+00 -1.000e+00 2.086e-16 1.000e+00 2.000e+00 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 1.000 1.581 0.632 0.54474 x 5.000 1.000 5.000 0.00105 ** --- Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 Residual standard error: 1.581 on 8 degrees of freedom Multiple R-Squared: 0.7576, Adjusted R-squared: 0.7273 F-statistic: 25 on 1 and 8 DF, p-value: 0.001053 This is R 2.4.1 on Mac OS X 10.4.8.
> - use R-help. This is really a question about R.
I think this could be a bug (at least it is not doing what I expected) so I emailed R-devel. Michael ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Received on Sat Dec 23 05:03:34 2006

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