R-alpha: expression(..) objects -- c(ex1, ex2) `fails'

Peter Dalgaard BSA p.dalgaard@kubism.ku.dk
03 Nov 1997 19:27:53 +0100

```Martin Maechler <maechler@stat.math.ethz.ch> writes:
[I've taken out the ">" citation symbols to allow cut and paste]

##-- `Simple'  length--1  expressions:
ex1 <- expression(hat(beta) == (X^t * X)^{-1} * X^t * y)
ex2 <- expression(bar(x) == sum(over(x[i], n), i==1, n))

##-- A length--2 expression:
ex12 <- expression(bar(x) == sum(over(x[i], n), i==1, n),
hat(x) == median(x[i], i==1,n))

> ###-> How could I take ex1, ex2 and "concat" them to an expression
> ###  of length 2 ?

#Heh. One would at least expect
l<-NULL
l[[1]]<-ex1[[1]]
l[[2]]<-ex2[[1]]
#to be a list of calls, which by definition is what an expression is,
#so you'd only need to change the mode, but:

mode(e)<-"expression"
e
# expression(list(hat(beta) == (X^t * X)^{
#         -1
# } * X^t * y, bar(x) == sum(over(x[i], n), i == 1, n)))

#(Why does it deparse in that strange way, BTW?)

#Also, textual representations of length-2 expressions is acting up:
deparse(ex12)
#[1] "bar(x) == sum(over(x[i], n), i == 1, n)"
str(ex12)
# bar(x) == sum(over(x[i], n), i == 1, n)
dput(ex12)
# bar(x) == sum(over(x[i], n), i == 1, n)
deparse(ex12[[2]])
# [1] "hat(x) == median(x[i], i == 1, n)"

--
O__  ---- Peter Dalgaard             Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics     2200 Cph. N
(*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907
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```