# [Rd] inconsistency or bug in coef() (PR#9358)

rmh at temple.edu rmh at temple.edu
Mon Nov 13 05:28:26 CET 2006

```tmp <- data.frame(x=c(1,1),
y=c(1,2))

tmp.lm <- lm(y ~ x, data=tmp)
summary(tmp.lm)

coef(summary(tmp.lm))

## I consider this to be a bug.  Since summary(tmp.lm) gives
## two rows for the coefficients, I believe the coef() function
## should also give two rows.

> summary(tmp.lm)

Call:
lm(formula = y ~ x, data = tmp)

Residuals:
1    2
-0.5  0.5

Coefficients: (1 not defined because of singularities)
Estimate Std. Error t value Pr(>|t|)
(Intercept)      1.5        0.5       3    0.205
x                 NA         NA      NA       NA

Residual standard error: 0.7071 on 1 degrees of freedom

> coef(summary(tmp.lm))
Estimate Std. Error t value  Pr(>|t|)
(Intercept)      1.5        0.5       3 0.2048328
>
> version
_
platform       i386-pc-mingw32
arch           i386
os             mingw32
system         i386, mingw32
status
major          2
minor          4.0
year           2006
month          10
day            03
svn rev        39566
language       R
version.string R version 2.4.0 (2006-10-03)
>

## this is a related problem

tmp <- data.frame(x=c(1,2),
y=c(1,2))

tmp.lm <- lm(y ~ x, data=tmp)
summary(tmp.lm)

coef(summary(tmp.lm))

## Here the summary() give NA for the values that can't be
## calculated and the coef() function gives NaN.  I think both
## functions should return the same result.

> summary(tmp.lm)

Call:
lm(formula = y ~ x, data = tmp)

Residuals:
ALL 2 residuals are 0: no residual degrees of freedom!

Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept)        0         NA      NA       NA
x                  1         NA      NA       NA

Residual standard error: NaN on 0 degrees of freedom
Multiple R-Squared:     1,      Adjusted R-squared:   NaN
F-statistic:   NaN on 1 and 0 DF,  p-value: NA

>
> coef(summary(tmp.lm))
Estimate Std. Error t value Pr(>|t|)
(Intercept)        0        NaN     NaN      NaN
x                  1        NaN     NaN      NaN
>
>

```